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Sample records for chloral hydrate

  1. Fate of 2,2,2-trichloroacetaldehyde (chloral hydrate) produced during trichloroethylene oxidation by methanotrophs.

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    Newman, L M; Wackett, L P

    1991-01-01

    Four different methanotrophs expressing soluble methane monooxygenase produced 2,2,2-trichloroacetaldehyde, or chloral hydrate, a controlled substance, during the oxidation of trichloroethylene. Chloral hydrate concentrations decreased in these cultures between 1 h and 24 h of incubation. Chloral hydrate was shown to be biologically transformed to trichloroethanol and trichloroacetic acid by Methylosinus trichosporium OB3b. At elevated pH and temperature, chloral hydrate readily decomposed an...

  2. Efficacy of Chloral Hydrate-Hydroxyzine and Chloral Hydrate-Midazolam in Pediatric Magnetic Resonance Imaging Sedation

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    Razieh FALLAH

    2014-04-01

    Full Text Available How to Cite This Article: Fallah R, Fadavi N, Behdad Sh, Fallah Tafti M. Efficacy of Chloral Hydrate-Hydroxyzine and Chloral Hydrate-Midazolam in Pediatric Magnetic Resonance Imaging Sedation. Iran J Child Neurol. 2014 Spring 8(2:11-17.ObjectiveMagnetic resonance imaging (MRI is a useful diagnostic tool for the evaluation of congenital or acquired brain lesions. But, in all of less than 8-year-old children, pharmacological agents and procedural sedation should be used to inducemotionless conditions for imaging studies. The purpose of this study was to compare the efficacy and safety of combination of chloral hydrate-hydroxyzine (CH+H and chloral hydrate-midazolam (CH+M in pediatric MRI sedation.Materials & MethodsIn a parallel single-blinded randomized clinical trial, sixty 1-7-year-old children who underwent brain MRI, were randomly assigned to receive chloral hydrate in a minimum dosage of 40 mg/kg in combination with either 2 mg/kg ofhydroxyzine or 0.5 mg/kg of midazolam. The primary outcomes were efficacy of adequate sedation (Ramsay sedation score of five and completion of MRI examination. The secondary outcome was clinical side-effects.ResultsTwenty-eight girls (46.7% and 32 boys (53.3% with the mean age of 2.72±1.58 years were studied. Adequate sedation and completion of MRI were achieved in 76.7% of CH+H group. Mild and transient clinical side-effects, such as vomiting of one child in each group and agitation in 2 (6.6 % children of CH+M group, were also seen. The adverse events were more frequent in CH+M group.ConclusionCombinations of chloral hydrate-hydroxyzine and chloral hydrate-midazolam were effective in pediatric MRI sedation; however, chloral hydrate-hydroxyzine was safer. References1. Lehman RK, Schor NF. Neurologic Evaluation. In:Kliegman RM, Stanton BF, Schor NF, St. Geme JW,Behrman RE, editors. Nelson Textbook of Pediatrics.19th ed. Philadelphia: Saunders; 2011. p. 2013-7.2. Sahyoun C, Krauss B. Clinical

  3. Chloral hydrate sedation in radiology: retrospective audit of reduced dose

    International Nuclear Information System (INIS)

    Chloral hydrate (CH) is safe and effective for sedation of suitable children. The purpose of this study was to assess whether adequate sedation is achieved with reduced CH doses. We retrospectively recorded outpatient CH sedations over 1 year. We defined standard doses of CH as 50 mg/kg (infants) and 75 mg/kg (children >1 year). A reduced dose was defined as at least 20% lower than the standard dose. In total, 653 children received CH sedation (age, 1 month-3 years 10 months), 42% were given a reduced initial dose. Augmentation dose was required in 10.9% of all children, and in a higher proportion of children >1 year (15.7%) compared to infants (5.7%; P 1 year (95.3%; P = 0.03). A reduced initial dose had no negative effect on outcome (P = 0.19) or time to sedation. No significant complications were seen. We advocate sedation with reduced CH doses (40 mg/kg for infants; 60 mg/kg for children >1 year of age) for outpatient imaging procedures when the child is judged to be quiet or sleepy on arrival. (orig.)

  4. Chloral hydrate sedation in radiology: retrospective audit of reduced dose

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    Bracken, Jennifer [Children' s University Hospital, Radiology Department, Dublin (Ireland); Royal Children' s Hospital, Department of Medical Imaging, Parkville, Victoria (Australia); Heaslip, Ingrid; Ryan, Stephanie [Children' s University Hospital, Radiology Department, Dublin (Ireland)

    2012-03-15

    Chloral hydrate (CH) is safe and effective for sedation of suitable children. The purpose of this study was to assess whether adequate sedation is achieved with reduced CH doses. We retrospectively recorded outpatient CH sedations over 1 year. We defined standard doses of CH as 50 mg/kg (infants) and 75 mg/kg (children >1 year). A reduced dose was defined as at least 20% lower than the standard dose. In total, 653 children received CH sedation (age, 1 month-3 years 10 months), 42% were given a reduced initial dose. Augmentation dose was required in 10.9% of all children, and in a higher proportion of children >1 year (15.7%) compared to infants (5.7%; P < 0.001). Sedation was successful in 96.7%, and more frequently successful in infants (98.3%) than children >1 year (95.3%; P = 0.03). A reduced initial dose had no negative effect on outcome (P = 0.19) or time to sedation. No significant complications were seen. We advocate sedation with reduced CH doses (40 mg/kg for infants; 60 mg/kg for children >1 year of age) for outpatient imaging procedures when the child is judged to be quiet or sleepy on arrival. (orig.)

  5. Percutaneous Absorption of Haloacetonitriles and Chloral Hydrate and Simulated Human Exposures

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    Trabaris, Maria; Laskin, Jeffrey D.; Weisel, Clifford P.

    2011-01-01

    Disinfection-by-products (DBPs) have long been a human health concern and many are known carcinogens and teratogens. Skin is exposed to DBPs in water through bathing and swimming; however, dermal uptake of many DBPs has not been characterized. The present studies were initiated to measure the permeation coefficients (Kp) for haloacetonitriles (HANs) and chloral hydrate (CH), important cytotoxic DBPs. The Kp values measured using fully hydrated dermatomed torso skin at 37 °C for the HANs range...

  6. Sleep Inducing for EEG Recording in Children: A Comparison between Oral Midazolam and Chloral Hydrate

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    Mahmoud Reza ASHRAFI

    2013-02-01

    Full Text Available How to Cite This Article: AshrafiMR, Azizi Malamiri R, Zamani GR, Mohammadi M, Hosseini F. Sleep Inducing for EEG Recording in Children: A Comparison between Oral Midazolam and Chloral Hydrate. Iran J Child Neurol. 2013 Winter;7(1:15-19.ObjectiveElectroencephalography (EEG recording is a long duration procedure that needs patient’s cooperation for device setup and performing the procedure. Many children lose their cooperation during this procedure. Therefore, sedation and sleep are frequently induced using a few agents as pre procedure medication in children before EEG recording. We aimed to compare the sedative effects of oral midazolam versus chloral hydrate before the procedure along with their impacts on EEG recording in children.Materials & MethodsA randomized trial was carried out to compare the sedative effects of oral midazolam versus chloral hydrate and their impacts on EEG recording in children. A total of 198 children (100 in the midazolam group and 98 in the chloral hydrate group were enrolled in the study and randomly allocated to receive either oral moidazolam or chloral hydrate.ResultsOral midazolam had superiority neither in sleep onset latency nor in sleep duration when compared to chloral hydrate. Moreover, the yield of epileptiform discharges in the chloral hydrate group was more than the midazolam group.ConclusionThe results of this study showed that both chloral hydrate 5% (one ml/kg and oral midazolam (0.5 mg/kg could be administered as a pre medication agent for EEG recording in children. However, oral midazolam at this dose had no advantage compared with chloral hydrate.ReferencesAshrafi MR, Mohammadi M, Tafarroji J, Shabanian R, Salamati P, Zamani GR. Melatonin versus chloral hydrate for recording sleep EEG. Eur J Paediatr Neurol 2010;14(3:235-8.Slifer KJ, Avis KT, Frutchey RA. Behavioral intervention to increase compliance with electroencephalographic procedures in children with developmental disabilities. Epilepsy

  7. Sleep/sedation in children undergoing EEG testing: a comparison of chloral hydrate and music therapy.

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    Loewy, Joanne; Hallan, Cathrine; Friedman, Eliezer; Martinez, Christine

    2006-12-01

    This study included a total of 60 pediatric patients ranging from 1 month through 5 years of age. The effects of chloral hydrate and music therapy were evaluated and compared as means of safe and effective ways to achieve sleep/sedation in infants and toddlers undergoing EEG testing. The results of the study indicate that music therapy may be a cost-effective, risk-free alternative to pharmacological sedation. PMID:17285817

  8. Sleep Inducing for EEG Recording in Children: A Comparison between Oral Midazolam and Chloral Hydrate

    OpenAIRE

    Mahmoud Reza ASHRAFI; Reza AZIZI MALAMIRI; Gholam Reza ZAMANI; Mahmoud MOHAMMADI; HOSSEINI, Firozeh

    2013-01-01

    How to Cite This Article: AshrafiMR, Azizi Malamiri R, Zamani GR, Mohammadi M, Hosseini F. Sleep Inducing for EEG Recording in Children: A Comparison between Oral Midazolam and Chloral Hydrate. Iran J Child Neurol. 2013 Winter;7(1):15-19.ObjectiveElectroencephalography (EEG) recording is a long duration procedure that needs patient’s cooperation for device setup and performing the procedure. Many children lose their cooperation during this procedure. Therefore, sedation and sleep are frequent...

  9. Effects of apomorphine upon local cerebral glucose utilization in conscious rats and in rats anesthetized with chloral hydrate

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    Grome, J.J.; McCulloch, J.

    1983-02-01

    The effects of the dopaminergic agonist apomorphine upon local cerebral glucose utilization in 43 anatomically discrete regions of the CNS were examined in conscious, lightly restrained rats and in rats anesthetized with chloral hydrate by means of the quantitative autoradiographic (/sup 14/C)2-deoxyglucose technique. In animals anesthetized with chloral hydrate, glucose utilization was reduced throughout all regions of the CNS from the levels observed in conscious animals. With chloral hydrate anesthesia, the proportionately most marked reductions in glucose use were noted in primary auditory nuclei, thalmaic relay nuclei, and neocortex, and the least pronounced reductions in glucose use (by 15-25% from conscious levels) were observed in limbic areas, some motor relay nuclei, and white matter. In conscious, lightly restrained rats, the administration of apomorphine effected significant increases in glucose utilization in 15 regions of the CNS, and significant reductions in glucose utilization in two regions of the CNS. In rats anesthetized with chloral hydrate, the effects of apomorphine upon local glucose utilization were less widespread and less marked than in conscious animals. The profound effects of chloral hydrate anesthesia upon local cerebral glucose use, and the modification by this anesthetic regime of the local metabolic responses to apomorphine, emphasize the difficulties which exists in the extrapolation of data from anesthetized animals to the conditions which prevail in the conscious animal.

  10. On cannabis, chloral hydrate, and career cycles of psychotropic drugs in medicine.

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    Snelders, Stephen; Kaplan, Charles; Pieters, Toine

    2006-01-01

    This article compares the careers of two psychotropic drugs in Western psychiatry, with a focus on the nineteenth century: Cannabis indica and chloral hydrate. They were used by doctors for similar indications, such as mania, delirium tremens, and what we would now call drug dependence. The two show similar career paths consisting of three phases: initial enthusiasm and therapeutic optimism; subsequent negative appraisal; and finally, limited use. These cycles, which we term "Seige cycles," are generally typical of the careers of psychotropic drugs in modern medicine. However, differences in the careers of both drugs are also established. The phases of chloral show relatively higher peaks and lower valleys than those of cannabis. Chloral is the first typically "modern" psychotropic drug; a synthetic, it was introduced in 1869 at a time of growing asylum populations, pharmaceutical interests, and high cultural expectations of scientific medicine. Cannabis indica, introduced in the 1840s, is typically a "premodern" drug steeped in the climate of cultural Romanticism. We conclude that the analytical concept of the Seige cycle is a useful tool for future research into drug careers in medicine. PMID:16549883

  11. Evidence for the Use of Isoflurane as a Replacement for Chloral Hydrate Anesthesia in Experimental Stroke: An Ethical Issue

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    Pétrault Maud

    2014-01-01

    Full Text Available Since an ethical issue has been raised regarding the use of the well-known anesthetic agent chloral hydrate, owing to its mutagenic and carcinogenic effects in animals, attention of neuroscientists has turned to finding out an alternative agent able to meet not only potency, safety, and analgesic efficacy, but also reduced neuroprotective effect for stroke research. The aim of this study was to compare the potential of chloral hydrate and isoflurane for both modulating the action of the experimental neuroprotectant MK801 and exerting analgesia. After middle cerebral artery occlusion in rats, no difference was observed in 24 h survival rate, success of ischemia, or infarct volume reduction between both anesthetics. However, isoflurane exerted a more pronounced analgesic effect than chloral hydrate as evidenced by formalin test 3 hours after anesthesia onset, thus encouraging the use of isoflurane in experimental stroke models.

  12. A survey of post-discharge side effects of conscious sedation using chloral hydrate in pediatric CT and MR imaging

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    Kao, S.C.; Adamson, S.D.; Tatman, L.H.; Berbaum, K.S. [Department of Radiology, Univ. of Iowa College of Medicine, Iowa City, IA (United States)

    1999-04-01

    Background. Limited information is available on post-discharge side effects of chloral hydrate sedation in pediatric imaging. Objective. To prospectively study the post-discharge side effects of chloral hydrate sedation in pediatric CT and MR imaging. Materials and methods. A total of 119 children undergoing CT and MRI were sedated using chloral hydrate with 89 % success (mean initial dose, 72 mg/kg body weight) and 98 % success after augmentation (mean total, 78 mg/kg body weight). The frequency of each post-discharge side effect was correlated with other side effects and 12 patient/technical parameters. Results. The survey was completed in 80 children. Sleepiness lasted for > 4 h in 28 %. Unsteadiness occurred in 68 % and hyperactivity in 29 %. Appetite became poor in 14 % and vomiting occurred in 15 %. Normal activity was resumed after > 4 h in 54 %. Sleep deprivation did not result in increased success or earlier onset of sedation and might be associated with hyperactivity. A higher dose did not result in an increased success rate or earlier onset of sedation within the dose range used in this study. Conclusion. Data on the post-discharge side effects of chloral hydrate sedation will be useful to radiologists, technologists, and nurses explaining to parents about sedation using this agent. (orig.) With 2 tabs., 24 refs.

  13. Chloral hydrate in pediatric magnetic resonance imaging: evaluation of a 10-year sedation experience administered by radiologists

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    Delgado, Jorge; Toro, Rodrigo; Rascovsky, Simon; Arango, Andres; Angel, Gabriel J.; Calvo, Victor; Delgado, Jorge A. [Fundacion Instituto de Alta Tecnologia Medica, Department of Radiology, Medellin (Colombia)

    2014-08-21

    Chloral hydrate is a sedative that has been used for magnetic resonance imaging (MRI). To evaluate the use, effectiveness and safety of chloral hydrate administered by radiologists for the sedation of children who require MRI procedures. We retrospectively reviewed the clinical charts for all patients ages 0 - 10 years old who underwent sedation with chloral hydrate for MRI from January 2000 to December 2010. Demographic factors, dose information, indication for MRI, therapeutic failures and adverse reactions to the drug were reviewed. One thousand, seven hundred and three children (946 males, 757 females) with a median age of 2.5 years (range: 4 days - 9.91 years) received chloral hydrate. Moderate to deep sedation was achieved in 1,618/1,703 (95%) of the patients, 35/1,703 (2.1%) of the patients failed to achieve moderate to deep sedation, and 47/1,703 (2.8%) of the patients woke up during MRI examination. Adverse reactions were present in 31/1,703 (1.8%) of the patients. Three severe adverse reactions occurred (0.18%). A single dose of chloral hydrate (40-60 mg/kg) was administered to 1,477/1,703 patients (86.7%). An additional dose of chloral hydrate (10-20 mg/kg), given 15 min after the first dose or when the patient woke up during the MRI examination, was required in 226/1,703 patients (13.3%). The likelihood of requiring an additional dose in children older than 2 years was 2.2 times the likelihood compared to children younger than 2 years (OR = 2.2 [95%CI: 1.6-3.0]). The use of a reduced dose (<50 mg/kg) was not associated with a higher therapeutic failure rate (OR = 1.04 [95%CI 0.57-1.89]). Chloral hydrate is an appropriate sedation option for pediatric patients in MRI services when strict patient selection criteria are met. The use of a reduced dose does not affect the effectiveness of sedation. The lack of data regarding the presence of transient oxygen desaturation, the time to induce sedation and the exact duration of sedation are limitations of this

  14. Sedative effect of oral diazepam and chloral hydrate in the dental treatment of children

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    Kantovitz Kamila

    2007-06-01

    Full Text Available Purpose : The purpose was to evaluate two sedation protocols during dental sessions in anxious children. Materials and Methods : It was a randomized and double-blind study, with each individual being his/her own control within each protocol. Furthermore, the two protocols were compared. Twenty children (36 to 84 months old who exhibited "definitely negative" behavior according to the Frankl scale were assigned to receive oral chloral hydrate (40 mg/kg (Group I or Diazepamβ (5 mg (Group II. Behavior during local anesthesia, application of rubber dam, cavity preparation, restorative procedures was evaluated, considering the degree of sleep, body movement, crying and overall behavior. Vital signs were assessed at three different times. The Wilcoxon, Mann-Whitney, Exact Fisher′s and Spearman correlation tests were used to analyze the data. Results : Group I presented higher scores for sleep during the CH session than placebo session during rubber dam application ( P = 0.0431 and restoration ( P = 0.0431. In Group II there was no statistically significant difference ( p > 0.05. There were no statistically significant differences between sessions and groups in the evaluation of body movement, crying and vital signs. Overall behavior in the placebo session was better than in the CH session during local anesthesia, but there was no difference between the two drug regimens. There was influence of age during anesthesia and cavity preparation in Group I and during rubber dam application in Group II. It was concluded that oral diazepam and chloral hydrate had no influence on the behavior management for dental treatment with the studied sample.

  15. The effects of apomorphine upon local cerebral glucose utilization in conscious rats and in rats anesthetized with chloral hydrate

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    Grome, J.J.; McCulloch, J.

    1983-02-01

    The effects of the dopaminergic agonist apomorphine (1 mg . kg-1 i.v.) upon local cerebral glucose utilization in 43 anatomically discrete regions of the CNS were examined in conscious, lightly restrained rats and in rats anesthetized with chloral hydrate by means of the quantitative autoradiographic (/sup 14/C)2-deoxyglucose technique. In animals anesthetized with chloral hydrate, glucose utilization was reduced throughout all regions of the CNS from the levels observed in conscious animals, although the magnitude of the reductions in glucose use displayed considerable regional heterogeneity. With chloral hydrate anesthesia, the proportionately most marked reductions in glucose use (by 40-60% from conscious levels) were noted in primary auditory nuclei, thalmaic relay nuclei, and neocortex, and the least pronounced reductions in glucose use (by 15-25% from conscious levels) were observed in limbic areas, some motor relay nuclei, and white matter. In conscious, lightly restrained rats, the administration of apomorphine (1 mg . kg-1) effected significant increased in glucose utilization in 15 regions of the CNS (e.g., subthalamic nucleus, ventral thalamic nucleus, rostral neocortex, substantia nigra, pars reticulata), and significant reductions in glucose utilization in two regions of the CNS (lateral habenular nucleus and anterior cingulate cortex).

  16. Percutaneous absorption of haloacetonitriles and chloral hydrate and simulated human exposures.

    Science.gov (United States)

    Trabaris, Maria; Laskin, Jeffrey D; Weisel, Clifford P

    2012-06-01

    Disinfection-by-products (DBPs) have long been a human health concern and many are known carcinogens and teratogens. Skin is exposed to DBPs in water through bathing and swimming; however, dermal uptake of many DBPs has not been characterized. The present studies were initiated to measure the permeation coefficients (K(p) ) for haloacetonitriles (HANs) and chloral hydrate (CH), important cytotoxic DBPs. The K(p) values measured using fully hydrated dermatomed torso skin at 37 °C for the HANs ranged from 0.099 to 0.17 cm h⁻¹, and was 0.0039 cm h⁻¹ for CH. Of the HANs, dibromoacetonitrile had the highest permeability while chloroacetonitrile had the lowest permeability and a direct relationship was observed between their K(p) and their octanol/water partition coefficients (K(ow) ). The K(p) values of the HANs were also approximately 30 times that of CH. The monthly dermal and ingestion doses of HANs and CH of an average American population were estimated using Monte Carlo simulations. The dermal doses of HANs from showering and bathing ranged from 0.39 to 0.78 times their ingestion doses but only approximately 0.02 times their ingestion doses for CH, assuming that the K(p) values determined are applicable to shorter water contact times. However, that ratio can vary markedly with chlorinated swimming pool exposures, with a range of 0.30-2.3 for HANs and 0.19-0.25 for CH. Dermal exposure to HANs and CH seems to be a significant route of exposure and should be considered when evaluating their total exposure during the routine usage of water for bathing and swimming. PMID:21365670

  17. Toxicokinetics of chloral hydrate in ad libitum-fed, dietary-controlled, and calorically restricted male B6C3F1 mice following short-term exposure

    International Nuclear Information System (INIS)

    Chloral hydrate is widely used as a sedative in pediatric medicine and is a by-product of water chlorination and a metabolic intermediate in the biotransformation of trichloroethylene. Chloral hydrate and its major metabolite, trichloroacetic acid, induce liver tumors in B6C3F1 mice, a strain that can exhibit high rates of background liver tumor incidence, which is associated with increased body weight. This report describes the influence of diet and body weight on the acute toxicity, hepatic enzyme response, and toxickinetics of chloral hydrate as part of a larger study investigating the carcinogenicity of chloral hydrate in ad libitum-fed and dietary controlled mice. Dietary control involves moderate food restriction to maintain the test animals at an idealized body weight. Mice were dosed with chloral hydrate at 0, 50, 100, 250, 500, and 1000 mg/kg daily, 5 days/week, by aqueous gavage for 2 weekly dosing cycles. Three diet groups were used: ad libitum, dietary control, and 40% caloric restriction. Both dietary control and caloric restriction slightly reduced acute toxicity of high doses of chloral hydrate and potentiated the induction of hepatic enzymes associated with peroxisome proliferation. Chloral hydrate toxicokinetics were investigated using blood samples obtained by sequential tail clipping and a microscale gas chromatography technique. It was rapidly cleared from serum within 3 h of dosing. Trichloroacetate was the major metabolite in serum in all three diet groups. Although the area under the curve values for serum trichloroacetate were slightly greater in the dietary controlled and calorically restricted groups than in the ad libitum-fed groups, this increase did not appear to completely account for the potentiation of hepatic enzyme induction by dietary restriction

  18. The use of oral pentobarbital sodium (Nembutal) versus oral chloral hydrate in infants undergoing CT and MR imaging - a pilot study

    International Nuclear Information System (INIS)

    Background. Chloral hydrate, a commonly used oral sedative for infants undergoing imaging examinations, has a bitter taste and requires relatively large volume, provoking unpleasant reactions from the infants. Experience with an alternative sedative, oral pentobarbital (Nembutal), has not been reported for infants Objective. To compare patient acceptance of oral Nembutal and oral chloral hydrate for sedation of infants up to 12 months of age. Methods and materials. Fifty-four infants (mean age: 7 months) were prospectively enrolled. Parents chose Nembutal, chloral hydrate, or no preference. Thirty-eight infants received Nembutal (4-6 mg/kg) mixed with cherry syrup and 16 received chloral hydrate (50-100 mg/kg). We recorded infant's acceptance of sedative, parental impression of infant's acceptance, time to sedation, time to discharge, adverse effects, parental preference of future sedative. Results. Infant acceptance and parental impression were better for Nembutal (P < 0.0001). Fewer parents in the Nembutal group preferred another sedative (P = 0.05). There was a trend toward shorter time to discharge with Nembutal (P = 0.03). There were no adverse effects in either group. One infant failed to sedate with Nembutal. Conclusions. Compared with chloral hydrate, oral Nembutal has significantly better acceptance by infants and parents, equal effectiveness, and may result in a shorter time to discharge. (orig.)

  19. Identification of some volatile endogenous constituents in rat brain tissue and the effects of lithium carbonate and chloral hydrate.

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    Politzer, I R; McDonald, L K; Laseter, J L

    1976-11-01

    Nine endogenous volatile compounds were found in rat brain tissue, and were identified by mass spectrometry as chloroform, a 5-C-aldehyde, dimethyl disulphide, 2,5-dimethyl tetrahydrofuran, a 8-C-alkane, xylene, 2-heptanone, heptaldehyde and 2-n-pentylfuran. Using gas chromatographic and gas chromatographic mass spectrometric techniques, it was established that lithium carbonate did not induce the production of detectable amounts of any new volatile compounds in brain tissue. However, after administration of chloral hydrate, trichloroethanol, a compound not normally present in rat brain tissue, was found to be present. PMID:996360

  20. Sedative Effect of Oral Midazolam/Hydroxyzine versus Chloral Hydrate/Hydroxyzine on 2-6 Year-Old Uncooperative Dental Patients: A Randomized Clinical Trial.

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    Masoud Fallahinejad Ghajari

    2014-02-01

    Full Text Available Different drugs are used for conscious sedation in pediatric dentistry either single or in combination. This study assessed the comparative effect of midazolam/hydroxyzine and chloral hydrate/hydroxyzine on 2-6 year-old uncooperative children needing dental treatment.A double blind cross-over randomized clinical trial was designed and 16 children aged 2-6 years with ASA1 status who were judged with negative to definitely negative behavior (according to Frankl were chosen. Cases were divided randomly into two groups. The first group received midazolam/hydroxyzine (MH at the first visit while the second group received chloral hydrate/hydroxyzine (CHH as the first medication. Both groups received the other regimen at the second visit. Midazolam 0.5mg/kg and chloral hydrate 50mg/kg with 1mg/kg hydroxyzine were administered. Cases were subsequently assessed for sedation and then dental treatment was performed. Blood oxygen saturation (SpO2 and pulse rate (PR were measured before and after drug administration, as well as during and after dental treatment. The Houpt scale was also used for the level of sedation before, during and after treatment. Data were analyzed using Wilcox-on signed rank test and the paired t-test.Sedative success rate was 64.3% in cases of MH and 33.3% in CHH. The difference between groups was significant (P=0.046. The success rate was significantly different between groups at different measurement stages as well (P<0.05. No difference was found on the child's behavior scale based on the type of drugs used first; this indicates no carry-over effect. Comparing the PR and SpO2 values at different readings showed no significant differences.Midazolam/hydroxyzine showed a significantly higher sedative effect than chloral hydrate/hydroxyzine in this study.

  1. Oral Chloral Hydrate Compare with Rectal Thiopental in Pediatric Procedural Sedation and Analgesia; a Randomized Clinical Trial

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    Reza Azizkhani

    2014-03-01

    Full Text Available Introduction: The increasing use of diagnostic imaging in pediatric medicine has resulted in growing need for procedural sedation and analgesia (PSA to minimize motion artifacts during procedures. The drug of choice in pediatric PSA was not introduced till now. The aim of the present study was comparison of oral chloral hydrate (OCH and rectal sodium thiopental (RST in pediatric PSA.Methods: In the present randomized clinical trial, 2-6 years old pediatrics who referred for performing brain computed tomography scan was enrolled and were randomly divided in to two groups. OCH (50mg/kg and RST (25mg/kg were prescribed and a trained nurse recorded the time from drug prescription to receiving the conscious sedation (onset of action, the total time period which the patient has the Ramsay score≥4 (duration of action, and adverse effect of agents. Mann-Whitney U test and chi-squared test, and Non-parametric analysis of covariance (ANCOVA were used for comparisons. Results: One hundred and forty children were entered to two groups of OCH and RST, randomly. The patients of two groups had similar age, sex, weight, and baseline vital signs except for diastolic blood pressure (p<0.001. The onset of action in OCH and RST groups were 24.5±6.1and 28.7±5.2 minutes, respectively (p<0.001. Duration of action in OCH and RST groups were 12.9±2.8 minutes and 13.7±2.6 minutes, respectively (p=0.085. Non parametric ANCOVA revealed that only diastolic blood pressure was affected by drug prescription (p=0.001. In 11(15.7% patients in RST group, diarrhea was observed during 24 hours (p=0.001. Oxygen desaturation was observed only in two patients, both in OCH group. Conclusion: Each of the sedative has advantages and disadvantages that should be considered when selecting one for inducing short-term sedation. It seems that rectal sodium thiopental and oral chloral hydrate are equally effective in pediatric PSA and based on patient’s condition we can administrate

  2. Towards optimized anesthesia protocols for stereotactic surgery in rats: Analgesic, stress and general health effects of injectable anesthetics. A comparison of a recommended complete reversal anesthesia with traditional chloral hydrate monoanesthesia.

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    Hüske, Christin; Sander, Svenja Esther; Hamann, Melanie; Kershaw, Olivia; Richter, Franziska; Richter, Angelika

    2016-07-01

    Although injectable anesthetics are still widely used in laboratory rodents, scientific data concerning pain and distress during and after stereotactic surgery are rare. However, optimal anesthesia protocols have a high impact on the quality of the derived data. We therefore investigated the suitability of recommended injectable anesthesia with a traditionally used monoanesthesia for stereotactic surgery in view of optimization and refinement in rats. The influence of the recommended complete reversal anesthesia (MMF; 0.15mg/kg medetomidine, 2mg/kg midazolam, 0.005mg/kg fentanyl; i.m.) with or without reversal and of chloral hydrate (430mg/kg, 3.6%, i.p.) on various physiological, biochemical and behavioral parameters (before, during, after surgery) was analyzed. Isoflurane was also included in stress parameter analysis. In all groups, depth of anesthesia was sufficient for stereotactic surgery with no animal losses. MMF caused transient exophthalmos, myositis at the injection site and increased early postoperative pain scores. Reversal induced agitation, restlessness and hypothermia. Even the low concentrated chloral hydrate led to peritonitis and multifocal liver necrosis, corresponding to increased stress hormone levels and loss in body weight. Increased stress response was also exerted by isoflurane anesthesia. Pronounced systemic toxicity of chloral hydrate strongly questions its further use in rodent anesthesia. In view of undesired effects of MMF and isoflurane, thorough consideration of anesthesia protocols for particular research projects is indispensable. Reversal should be restricted to emergency situations. Our data support further refinement of the current protocols and the importance of sham operated controls. PMID:27067188

  3. 误服大剂量水合氯醛致新生儿呼吸暂停%Apnea in a neonate due to mistaken high-dose chloral hydrate

    Institute of Scientific and Technical Information of China (English)

    李英; 刘莹; 史强; 王晓玲

    2015-01-01

    1例25日龄男性新生儿因疑诊先天性心脏病欲行心脏超声检查,医师开具水合氯醛合剂10 ml,注明检查前口服2 ml.患儿家长取药时药师仅口头交代给患儿口服2 ml,而未书面标明用法用量.检查前,患儿家长将10ml水合氯醛全部给患儿服下,导致患儿在超声检查期间出现呼吸暂停.给予气管插管及静脉滴注氨茶碱.次日改为鼻导管吸氧.6d后,患儿病情好转.%A 25-day-old male neonate suspected of having congenital heart disease underwent echocardiographic examination.The physician prescribed chloral hydrate mixture 10 ml, oral 2 ml before the examination.The pharmacist just told to take 2 ml, without written dosage indication.Before the ultrasound examination, the parent administered the newborn 10 ml chloral hydrate mixture, and then, he developed apnea during the examination.He received tracheal intubation and intravenous infusion of aminophylline.The next day, he was given oxygen inhalation through nasal tube.Six days later, the infant's condition was improved.

  4. Enhancement of gamma-ray-induced mutation frequency in rice by post-treatment with chloral hydrate, methanol and their mixtures with ethanol

    International Nuclear Information System (INIS)

    An evaluation has been made of the mutagenic activity of ethanol, chlorate hydrate (CH) and methanol on rice seed. In independent treatments with ethanol, methanol, CH and four aqueous mixtures of these chemicals, chlorophyll-deficient mutants were not recovered in the M2 generation. However, in sequential treatments with gamma rays + CH, gamma rays + methanol and gamma rays + aqueous mixtures of these chemicals, significant increases in the yields of chlorophyll mutations were observed as compared to that of a 30 kR gamma ray treatment. In contrast, post-irradiation treatment with ethanol failed to provoke any increase in the frequency of chlorophyll mutants in the M2 generation. The results indicate that CH and methanol alone and mixed with ethanol can potentiate gamma ray-induced genetic lesions in rice seed. (author)

  5. Effects of Chloral Hydrate and Atracurium Besilate on Compound Muscle Action Potential of Sciatic Nerves in Rats%水合氯醛和苯磺酸阿曲库铵对大鼠坐骨神经复合肌肉动作电位的影响

    Institute of Scientific and Technical Information of China (English)

    孟祥虎; 臧光辉; 樊龙昌; 肖海涛; 权伟合; 刘继红; 张传汉; 罗爱林; 田玉科

    2012-01-01

    目的:研究水合氯醛和苯磺酸阿曲库铵对大鼠坐骨神经复合肌肉动作电位(compound muscle action potential,CMAP)的影响.方法:成年SD大鼠20只,随机分为2组(n=10):水合氯醛组(C组)和水合氯醛复合苯磺酸阿曲库铵组(CA组).2组腹腔注射7%水合氯醛350 mg·kg-1麻醉,给予水合氯醛后8 min时CA组腹腔注射苯磺酸阿曲库铵2.5 μg·kg-1.于给予水合氯醛8 min时刺激坐骨神经,记录其所支配的腓肠肌的CMAP.刺激强度为0.50 v、0.55 v、0.60 v,波宽0.05 ms,频率10 Hz,每隔5 min重复上述刺激.结果:与8 min时比较,0.50 v,0.55 v,0.60 v强度下C组CMAP的峰峰值及潜伏期均无明显变化(P均>0.05);CA组与8 min时比较,0.50,0.55 及0.60 v强度下23~43 min时的CMAP峰峰值降低(P<0.05或0.01),0.50 v强度下38 min的CMAP潜伏期延长(P<0.05),0.55 v,0.60 v强度下,23~43 min的CMAP潜伏期延长(P<0.05或0.01).结论:水合氯醛对大鼠坐骨神经CMAP无明显影响;而复合肌松药苯磺酸阿曲库铵后对CMAP有一过性的抑制作用.%Objective: To study the effects of chloral hydrate with or without atracurium besilate on compound muscle action potential ( CMAP ) of sciatic nerves in rats. Method: Twenty adult SD rats were randomly divided into chloral hydrate group ( group C ) and chloral hydrate with atracurium besilate group ( group CA ). Group C was treated by chloral hydrate, and group CA was treated with chloral hydrate and atracurium besilate. Both the groups were anesthetized by intraperitoneal injection of 7% chloral hydrate with the dosage of 350 mg·kg-1. After 8min of successful anesthesia, group CA was intraperitoneally infused with atracurium besilate (2.5 μg ·kg-1). Meanwhile, the two groups were stimulated sciatic nerves with stimulus intensity of 0.50 v, 0.55 v and 0.60 v, width of 0. 05 ms and frequency of 10 Hz, respectively. Each stimulus repeated three times every 5 min. Result: In group C, the peak to peak values and incubation

  6. Comparison of clinical application on EEG evoked by sleep between Diphenhydramine and chloral hydrate in children medicine%苯海拉明与水合氯醛在诱导小儿睡眠脑电图中的应用比较

    Institute of Scientific and Technical Information of China (English)

    刘文萍; 李爱红; 冉巧萍

    2012-01-01

    Objective Comparison the difference between Diphenhydramine and chloral hydrate on EEG evoked by sleep in children medicine. Methods 86 child patients with clinically diagnosed epilepsy were classified as Diphenhydramine group (43 cases) and chloral hydrate group (43cases).they were examined on EEG evoked by sleep separately , with the epilptiform discharges (NREM) in sleeping phase I and sleeping phase II were observed respectively. Results the positive results in diphenhydramine group were 31 cases (72.0%). In chloral hydrate group were 22 cases (55.1%),χ2=3.983,P0.05. Conclusions The EEG evoked by sleep with Diphenhydramine discharges of the two groups mainly in sleep phase I and II. Diphenhydramine should regard as the drug of choice for child patients on EEG evoked in sleep.%目的:比较苯海拉明与水合氯醛在小儿药物诱发睡眠脑电图(EEG)中癫痫波阳性检出率的差异.方法:对86例临床诊断为癫痫的患儿随机分为苯海拉明组(43例)及水合氯醛(43例),分别进行睡眠诱发脑电图(EEG)检查,同时观察两组异常放电在非快速动眼(NREM)睡眠Ⅰ,Ⅱ期的出现率.结果:苯海拉明组阳性31例(72%),水合氯醛组阳性22例(51.1%). x2=3.982,P<0.05. (NREM)睡眠Ⅰ,Ⅱ期异常放电出现率:苯海拉明组1 9例(88.5%),水合氯醛组12例(75.0%).x2=1.024,P>0.05.结论:苯海拉明较水合氯醛诱发癫痫波阳性率高,两组异常放电均以(NREM)睡眠Ⅰ,Ⅱ期为主.苯海拉明应作为小儿诱发睡眠首选药物之一.

  7. Influence of different time of chloral hydrate delivery on the hypnosis of children with pulmonary function test%水合氯醛不同时间给药对行肺功能检查患儿催眠作用的影响

    Institute of Scientific and Technical Information of China (English)

    张敏艳; 王芳; 袁远

    2012-01-01

    Objective To study the effect of the 10% of chloral hydrate delivery in different time on the children before they receive the pulmonary function test so as to discuss clinical effects.Methods Totals of two hundred children with asthma or asthmatic bronchitis needed the pulmonary function test were recruited,and randomly divided into experience group and control group with each group one hundred cases.Experience group received the chloral hydrate to hypnosis in ten to thirty minutes before they fall asleep,while control group received in doctor' s advice or appointment time.Then,the time of falling asleep,sleep level,the situation of test finishing in two group were observed and compared.Results The effective rate of chloral hydrate in experience group was 98% which was significantly higher than 70% in control group( P < 0.01 )and there was significant differenee between two groups in the time of falling asleep and the sedation effect among the different ages (P<0.01).Conclusions Personal medicine delivery can get the better effect,which is chloral hydrate delivery according to the sleep cycles of children before they receive the pulmonary function test.%目的 观察肺功能检查前10%的水合氯醛不同时间点给药方法对不同年龄患儿的催眠效果,讨论其临床疗效.方法 选取200例哮喘、喘息性支气管炎需做肺功能检查的患儿随机分为实验组和对照组各100例,实验组选择患儿入睡前10 ~30 min应用水合氯醛进行催眠,对照组选择按常规执行医嘱时间或按预约的时间应用水合氯醛,比较两组患儿用药后入睡的时间、程度,是否完成肺功能榆查.结果 实验组应用水合氯醛后有效率为98%高于对照组的70%,差异有统计学意义(Z=6.1389,P<0.01);不同年龄阶段的患儿应用水合氯醛灌肠后入睡时间及镇静效果实验组均优于对照组,差异均有统计学意义(Z分别为3.175 2,3.963 5,2.850 1,4.888 8;P<0.01).结论

  8. 吹扫捕集气相色谱质谱法测定水中的三氯乙醛%Purge and Trap-Gas Chromatography Mass Spectrometry Determination of Chloral in Drinking water

    Institute of Scientific and Technical Information of China (English)

    王敏捷; 曹立峰; 袁润蕾; 来克冰

    2013-01-01

      本文采用吹扫捕集气相色谱质谱法对水中的三氯乙醛进行测定。研究了碱性条件下反应温度与反应时间对三氯乙醛转化速度的影响。标准曲线范围在 1~50μg/L 时,所得三氯乙醛的线性相关系数为 0.9999。回收率为 97.0%~99.8%,RSD 为 0.9%。该法回收率高、精密度好、准确度好,且操作简便、快速,适用于水中三氯乙醛的分析。%Established the purge and trap-gas chromatography mass spectrometry determination of chloral in water. Study on reaction temperature and reaction time under alkaline conditions on the transformation effect of chloral hydrate. The linear correlation coefficient was 0.9999 when the standard curve in the range of 1 ~50µ g/L, The recovery was 97% ~ 99.8% and RSD was 0.9%. The method has high recovery rate and good precision, good accuracy, simple operation, fast, suitable for actual analysis.

  9. Trihalomethane, haloacetonitrile, and chloral hydrate formation potentials of organic carbon fractions from sub-tropical forest soils.

    Science.gov (United States)

    Zhang, Qian; Kuang, Wan-fang; Liu, Lu-ying; Li, Kexin; Wong, Kin-hang; Chow, Alex T; Wong, Po-keung

    2009-12-30

    Forest landscapes represent the major land-cover type for the watersheds of the East River, which is the source of water for 40 million people in South China. Forest soils with high levels of organic carbon are a potential terrestrial source of dissolved organic carbon (DOC) into the East River. DOC is of great concern, since it can form carcinogenic disinfection byproducts (DBPs) during drinking water treatment. In this study, soils from three altitudes (200, 450 and 900 m) in the Xiangtou Mountain Nature Reserve in South China, representing soils from evergreen moon forest, transitional evergreen broadleaf forest, and evergreen broadleaf forest, respectively, were evaluated for their potential contributions of DBP precursors into the East River. The water extractable organic carbon (WEOC) in three forest soils was physically and chemically fractionated into particulate organic carbon (1.2-0.45 microm), colloidal organic carbon (0.45-0.22 microm), and dissolved organic carbon (DOC) (soils were incubated at 15, 25 and 35 degrees C for 14d in darkness to examine the impact of temperature effects on the availability and characteristics of WEOC. The extraction study showed that the amount of WEOC was proportional to soil organic carbon content, of which about 1% was water extractable. Regardless of soil type, DOC and HPOA were the most reactive fractions in forming THMs, CHD, and HANs. Production of DOC and HPOA in WEOC increased over 14 d incubation as incubation temperature increased, but the temperature did not alter the distribution of physical and chemical fractions and their reactivity in DBP formation. Results suggest higher inputs of DOC and DBP precursors from forest watersheds into source water may result in a warmer environment. PMID:19695772

  10. Gas hydrates

    Digital Repository Service at National Institute of Oceanography (India)

    Ramprasad, T.

    Content-Type text/plain; charset=UTF-8 43 Gas Hydrates T. Ramprasad National Institute of Oceanography, Dona Paula, Goa-403 004 rprasad@nio.org A gas hydrate is a crystalline solid; its building blocks consist of a gas molecule... surrounded by a cage of water molecules. Thus it is similar to ice, except that the crystalline structure is stabilized by the guest gas molecule within the cage of water molecules. Many gases have molecular sizes suitable to form hydrate, including...

  11. Natural Gas Hydrates

    OpenAIRE

    Ersland, Geir

    2010-01-01

    The experimental set-up with the MRI monitoring apparatus was capable of forming large quantities of methane hydrates in sandstone pores and monitor hydrate growth patterns for various initial conditions. Spontaneous conversion of methane hydrate to carbon dioxide hydrate occurred when methane hydrate, in porous media, was exposed to liquid carbon dioxide. The MRI images did not detect any significant increase in signal in the hydrate saturated cores that would indicate the presence of free w...

  12. Uncertainty Evaluation of Determination of Chloral in Water with GC/MS%GC/MS测定水中三氯乙醛的不确定度评定

    Institute of Scientific and Technical Information of China (English)

    杭培红; 徐巍

    2012-01-01

    系统介绍了吹扫捕集气相色谱/质谱法测定水中三氯乙醛不确定度评定过程,对吹扫捕集气相色谱/质谱法测定水中三氯乙醛的测定过程进行分析,通过数学模型分析并计算测试过程中的不确定度分量,最后计算出相对合成标准不确定度和相对扩展不确定度。结果表明,吹扫捕集气相色谱/质谱法测定水中三氯乙醛的不确定度主要有四个来源:标准样品浓度及稀释过程,标准曲线及回归偏差,样品取样量,仪器稳定性。%The uncertainty of determining chloral in water was evaluated by purge and trap-gas chromatography-mass spectrometry(purge trap-GC-MS).The determination process of chloral in water was analyzed by purge trap-GC-MS.The uncertainty factors in analyzing process were determined and calculated by mathematic model,and the relative synthesis standard uncertainty and the relative expansion standard uncertainty were calculated out.The four main sources were the uncertainty of standard samples and by dilution process,the uncertainty of linear and regression variance,the uncertainty brought in the sampling process,and the uncertainty resulted from the instrument stability of purge trap-GC-MS.Four main sources of the uncertainty of determining chloral in water by purge trap-GC-MS was determined.The uncertainty evaluation process of determining chloral in water by purge trap-GC-MS was introduced systematically.

  13. HYDRATION AND ENZYME ACTIVITY

    OpenAIRE

    Poole, P.

    1984-01-01

    Hydration induced conformation and dynamic changes are followed using a variety of experimental techniques applied to hen egg white lysozyme. These changes are completed just before the onset of enzyme activity, which occurs before all polar groups are hydrated, and before monolayer coverage is attained. We suggest that these hydration induced changes are necessary for the return of enzyme activity.

  14. Gas hydrate nucleation

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-12-31

    The overall aim of the project was to gain more knowledge about the kinetics of gas hydrate formation especially the early growth phase. Knowledge of kinetics of gas hydrate formation is important and measurements of gas hydrate particle size and concentration can contribute to improve this knowledge. An experimental setup for carrying out experimental studies of the nucleation and growth of gas hydrates has been constructed and tested. Multi wavelength extinction (MWE) was the experimental technique selected for obtaining particle diameter and concentration. The principle behind MWE is described as well as turbidity spectrum analysis that in an initial stage of the project was considered as an alternative experimental technique. Details of the experimental setup and its operation are outlined. The measuring cell consists of a 1 litre horizontal tube sustaining pressures up to 200 bar. Laser light for particle size determination can be applied through sapphire windows. A description of the various auxiliary equipment and of another gas hydrate cell used in the study are given. A computer program for simulation and analysis of gas hydrate experiments is based on the gas hydrate kinetics model proposed by Skovborg and Rasmussen (1993). Initial measurements showed that knowledge of the refractive index of gas hydrates was important in order to use MWE. An experimental determination of the refractive index of methane and natural gas hydrate is described. The test experiments performed with MWE on collectives of gas hydrate particles and experiments with ethane, methane and natural gas hydrate are discussed. Gas hydrate particles initially seem to grow mainly in size and at latter stages in number. (EG) EFP-94; 41 refs.

  15. Hydration Assessment of Athletes

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    @@ KEY POINTS · Although there is no scientific consensus for 1 ) howbest to assess the hydration status of athletes, 2)what criteria to use as acceptable outcome measurements, or 3) the best time to apply practical assessment methods, there are methods that can be used toprovide athletes with useful feedback about their hydration status

  16. Withdrawing Nutrition, Hydration

    Science.gov (United States)

    Module eleven of the EPEC-O Self-Study Original Version discusses the general aspects of withholding or withdrawing of life-sustaining therapies, and presents a specific application to artificial nutrition and hydration.

  17. Hydrate morphology: Physical properties of sands with patchy hydrate saturation

    Science.gov (United States)

    Dai, S.; Santamarina, J.C.; Waite, William F.; Kneafsey, T.J.

    2012-01-01

    The physical properties of gas hydrate-bearing sediments depend on the volume fraction and spatial distribution of the hydrate phase. The host sediment grain size and the state of effective stress determine the hydrate morphology in sediments; this information can be used to significantly constrain estimates of the physical properties of hydrate-bearing sediments, including the coarse-grained sands subjected to high effective stress that are of interest as potential energy resources. Reported data and physical analyses suggest hydrate-bearing sands contain a heterogeneous, patchy hydrate distribution, whereby zones with 100% pore-space hydrate saturation are embedded in hydrate-free sand. Accounting for patchy rather than homogeneous hydrate distribution yields more tightly constrained estimates of physical properties in hydrate-bearing sands and captures observed physical-property dependencies on hydrate saturation. For example, numerical modeling results of sands with patchy saturation agree with experimental observation, showing a transition in stiffness starting near the series bound at low hydrate saturations but moving toward the parallel bound at high hydrate saturations. The hydrate-patch size itself impacts the physical properties of hydrate-bearing sediments; for example, at constant hydrate saturation, we find that conductivity (electrical, hydraulic and thermal) increases as the number of hydrate-saturated patches increases. This increase reflects the larger number of conductive flow paths that exist in specimens with many small hydrate-saturated patches in comparison to specimens in which a few large hydrate saturated patches can block flow over a significant cross-section of the specimen.

  18. PART II. HYDRATED CEMENTS

    Directory of Open Access Journals (Sweden)

    Milan Drabik

    2014-09-01

    Full Text Available Essential focus of the study has been to acquire thermoanalytical events, incl. enthalpies of decompositions - ΔH, of technological materials based on two types of Portland cements. The values of thermoanalytical events and also ΔH of probes of technological compositions, if related with the data of a choice of minerals of calcium-silicate-sulfate-aluminate hydrates, served as a valued input for the assessment of phases present and phase changes due to the topical hydraulic processes. The results indicate mainly the effects of "standard humidity" or "wet storage" of the entire hydration/hydraulic treatment, but also the presence of cement residues alongside calcium-silicate-sulfate-aluminate hydrates (during the tested period of treatment. "A diluting" effect of unhydrated cement residues upon the values of decomposition enthalpies in the studied multiphase system is postulated and discussed

  19. Protein hydration and dynamics

    International Nuclear Information System (INIS)

    Inelastic neutron scattering can measure the protein thermal fluctuations under the physiological aqueous environment, especially it is powerful to observe the low-energy protein dynamics in THz region, which are revealed theoretically to be coupled with solvations. Neutron enables the selective observation of protein and hydration water by deuteration. The complementary analysis with molecular dynamics simulation is also effective for the study of protein hydration. Some examples of the application toward the understanding of molecular basis of protein functions will be introduced. (author)

  20. Formation of porous gas hydrates

    CERN Document Server

    Salamatin, Andrey N

    2015-01-01

    Gas hydrates grown at gas-ice interfaces are examined by electron microscopy and found to have a submicron porous texture. Permeability of the intervening hydrate layers provides the connection between the two counterparts (gas and water molecules) of the clathration reaction and makes further hydrate formation possible. The study is focused on phenomenological description of principal stages and rate-limiting processes that control the kinetics of the porous gas hydrate crystal growth from ice powders. Although the detailed physical mechanisms involved in the porous hydrate formation still are not fully understood, the initial stage of hydrate film spreading over the ice surface should be distinguished from the subsequent stage which is presumably limited by the clathration reaction at the ice-hydrate interface and develops after the ice grain coating is finished. The model reveals a time dependence of the reaction degree essentially different from that when the rate-limiting step of the hydrate formation at...

  1. Modeling Hydrates and the Gas Hydrate Markup Language

    OpenAIRE

    Wang, Weihua; Moridis, George; Wang, Runqiang; Xiao, Yun; Li, Jianhui

    2007-01-01

    Natural gas hydrates, as an important potential fuels, flow assurance hazards, and possible factors initiating the submarine geo-hazard and global climate change, have attracted the interest of scientists all over the world. After two centuries of hydrate research, a great amount of scientific data on gas hydrates has been accumulated. Therefore the means to manage, share, and exchange these data have become an urgent task. At present, metadata (Markup Language) is recognized as one of the mo...

  2. Gas hydrates of Lake Baikal

    OpenAIRE

    Khlystov, O.; De Batist, M.; Shoji, H; Nishio, S.; L. Naudts; J. Poort

    2011-01-01

    This paper reviews some of the results of recent gas-hydrate studies in Lake Baikal, the only fresh-water lake in the world containing gas hydrates in its sedimentary infill. We give a historical overview of the different investigations and discoveries and highlight some recent breakthroughs in our understanding of the Baikal hydrate system. The importance of mapping mud volcanoes and gas seeps is stressed, as these are currently the only locations where gas hydrates at or very close to the f...

  3. Hydration and physical performance.

    Science.gov (United States)

    Murray, Bob

    2007-10-01

    There is a rich scientific literature regarding hydration status and physical function that began in the late 1800s, although the relationship was likely apparent centuries before that. A decrease in body water from normal levels (often referred to as dehydration or hypohydration) provokes changes in cardiovascular, thermoregulatory, metabolic, and central nervous function that become increasingly greater as dehydration worsens. Similarly, performance impairment often reported with modest dehydration (e.g., -2% body mass) is also exacerbated by greater fluid loss. Dehydration during physical activity in the heat provokes greater performance decrements than similar activity in cooler conditions, a difference thought to be due, at least in part, to greater cardiovascular and thermoregulatory strain associated with heat exposure. There is little doubt that performance during prolonged, continuous exercise in the heat is impaired by levels of dehydration >or= -2% body mass, and there is some evidence that lower levels of dehydration can also impair performance even during relatively short-duration, intermittent exercise. Although additional research is needed to more fully understand low-level dehydration's effects on physical performance, one can generalize that when performance is at stake, it is better to be well-hydrated than dehydrated. This generalization holds true in the occupational, military, and sports settings.

  4. Some thermodynamical aspects of protein hydration water

    Energy Technology Data Exchange (ETDEWEB)

    Mallamace, Francesco, E-mail: francesco.mallamace@unime.it [Dipartimento di Fisica e Scienze della Terra, Università di Messina and CNISM, I-98168 Messina (Italy); Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Center for Polymer Studies and Department of Physics, Boston University, Boston, Massachusetts 02215 (United States); Corsaro, Carmelo [Dipartimento di Fisica e Scienze della Terra, Università di Messina and CNISM, I-98168 Messina (Italy); CNR-IPCF, Viale F. Stagno D’Alcontres 37, I-98158 Messina (Italy); Mallamace, Domenico [Dipartimento SASTAS, Università di Messina, I-98166 Messina (Italy); Vasi, Sebastiano [Dipartimento di Fisica e Scienze della Terra, Università di Messina and CNISM, I-98168 Messina (Italy); Vasi, Cirino [CNR-IPCF, Viale F. Stagno D’Alcontres 37, I-98158 Messina (Italy); Stanley, H. Eugene [Center for Polymer Studies and Department of Physics, Boston University, Boston, Massachusetts 02215 (United States); Chen, Sow-Hsin [Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

    2015-06-07

    We study by means of nuclear magnetic resonance the self-diffusion of protein hydration water at different hydration levels across a large temperature range that includes the deeply supercooled regime. Starting with a single hydration shell (h = 0.3), we consider different hydrations up to h = 0.65. Our experimental evidence indicates that two phenomena play a significant role in the dynamics of protein hydration water: (i) the measured fragile-to-strong dynamic crossover temperature is unaffected by the hydration level and (ii) the first hydration shell remains liquid at all hydrations, even at the lowest temperature.

  5. Flow assurance intervention, hydrates remediation

    Energy Technology Data Exchange (ETDEWEB)

    Mancini, Christopher S. [Oceaneering International Inc., Houston, TX (United States)

    2012-07-01

    This paper addresses the issues of removing hydrates in sub sea flow lines and associated equipment with an Remotely Operated Vehicle (ROV) of opportunity and a multi-service-vessel (MSV). The paper is split into three topics: the equipment used with the ROV, assessing the interface points and handling fluids produced from drawing down the pressure. Each section is explained thoroughly and backed up with real world experience. The equipment section details information from actual jobs performed and why the particular components were utilized. The system is generally contained in an ROV mounted skid. Pumps are utilized to draw down the pressure inside the hydrated section of equipment, removing one of the three necessary components for hydrates formation. Once the section is pumped down, several options exist for handling the fluids pumped out of the system: pumping to surface, re-injection into the well, or injection into an operating flow line. This method of hydrates remediation is both economical and timely. Hydrate blockages form in low temperatures and high pressures. Reducing the pressure or increasing the temperature so the conditions lie to the right of the hydrate dissociation curve will slowly decompose the blockage. Depressurization and the use of MEG or methanol will give favorable conditions to remove the hydrate plug. Oceaneering has the capabilities to remove hydrates using the FRS in conjunction with an installation vessel to dispose of the gas and fluid removed from the flow line. Hydrate remediation techniques should be implemented into the initial design to reduce costs later. The cost of stopped production combined with the day rate for equipment needed for hydrate removal outweighs the costs if no technique is utilized. (author)

  6. Understanding silicate hydration from quantitative analyses of hydrating tricalcium silicates.

    Science.gov (United States)

    Pustovgar, Elizaveta; Sangodkar, Rahul P; Andreev, Andrey S; Palacios, Marta; Chmelka, Bradley F; Flatt, Robert J; d'Espinose de Lacaillerie, Jean-Baptiste

    2016-01-01

    Silicate hydration is prevalent in natural and technological processes, such as, mineral weathering, glass alteration, zeolite syntheses and cement hydration. Tricalcium silicate (Ca3SiO5), the main constituent of Portland cement, is amongst the most reactive silicates in water. Despite its widespread industrial use, the reaction of Ca3SiO5 with water to form calcium-silicate-hydrates (C-S-H) still hosts many open questions. Here, we show that solid-state nuclear magnetic resonance measurements of (29)Si-enriched triclinic Ca3SiO5 enable the quantitative monitoring of the hydration process in terms of transient local molecular composition, extent of silicate hydration and polymerization. This provides insights on the relative influence of surface hydroxylation and hydrate precipitation on the hydration rate. When the rate drops, the amount of hydroxylated Ca3SiO5 decreases, thus demonstrating the partial passivation of the surface during the deceleration stage. Moreover, the relative quantities of monomers, dimers, pentamers and octamers in the C-S-H structure are measured. PMID:27009966

  7. Understanding silicate hydration from quantitative analyses of hydrating tricalcium silicates

    Science.gov (United States)

    Pustovgar, Elizaveta; Sangodkar, Rahul P.; Andreev, Andrey S.; Palacios, Marta; Chmelka, Bradley F.; Flatt, Robert J.; D'Espinose de Lacaillerie, Jean-Baptiste

    2016-03-01

    Silicate hydration is prevalent in natural and technological processes, such as, mineral weathering, glass alteration, zeolite syntheses and cement hydration. Tricalcium silicate (Ca3SiO5), the main constituent of Portland cement, is amongst the most reactive silicates in water. Despite its widespread industrial use, the reaction of Ca3SiO5 with water to form calcium-silicate-hydrates (C-S-H) still hosts many open questions. Here, we show that solid-state nuclear magnetic resonance measurements of 29Si-enriched triclinic Ca3SiO5 enable the quantitative monitoring of the hydration process in terms of transient local molecular composition, extent of silicate hydration and polymerization. This provides insights on the relative influence of surface hydroxylation and hydrate precipitation on the hydration rate. When the rate drops, the amount of hydroxylated Ca3SiO5 decreases, thus demonstrating the partial passivation of the surface during the deceleration stage. Moreover, the relative quantities of monomers, dimers, pentamers and octamers in the C-S-H structure are measured.

  8. Investigation on Gas Storage in Methane Hydrate

    Institute of Scientific and Technical Information of China (English)

    Zhigao Sun; Rongsheng Ma; Shuanshi Fan; Kaihua Guo; Ruzhu Wang

    2004-01-01

    The effect of additives (anionic surfactant sodium dodecyl sulfate (SDS), nonionic surfactant alkyl polysaccharide glycoside (APG), and liquid hydrocarbon cyclopentane (CP)) on hydrate induction time and formation rate, and storage capacity was studied in this work. Micelle surfactant solutions were found to reduce hydrate induction time, increase methane hydrate formation rate and improve methane storage capacity in hydrates. In the presence of surfactant, hydrate could form quickly in a quiescent system and the energy costs of hydrate formation were reduced. The critical micelle concentrations of SDS and APG water solutions were found to be 300× 10-6 and 500× 10-6 for methane hydrate formation system respectively. The effect of anionic surfactant (SDS) on methane storage in hydrates is more pronounced compared to a nonionic surfactant (APG). CP also reduced hydrate induction time and improved hydrate formation rate, but could not improve methane storage in hydrates.

  9. Understanding silicate hydration from quantitative analyses of hydrating tricalcium silicates

    OpenAIRE

    Pustovgar, Elizaveta; Sangodkar, Rahul P.; Andreev, Andrey S.; Palacios, Marta; Chmelka, Bradley F.; Robert J. Flatt; D'Espinose De Lacaillerie, Jean-Baptiste

    2016-01-01

    Silicate hydration is prevalent in natural and technological processes, such as, mineral weathering, glass alteration, zeolite syntheses and cement hydration. Tricalcium silicate (Ca3SiO5), the main constituent of Portland cement, is amongst the most reactive silicates in water. Despite its widespread industrial use, the reaction of Ca3SiO5 with water to form calcium-silicate-hydrates (C-S-H) still hosts many open questions. Here, we show that solid-state nuclear magnetic resonance measuremen...

  10. Hydration in soccer: a review

    OpenAIRE

    Monteiro Cristiano Ralo; Guerra Isabela; Barros Turíbio Leite de

    2003-01-01

    Hydration should be considered before, during and after the exercise. This review intends to approach the main points of hydration process in soccer. The replacement of fluids during exercise is proportional to some factors, such as: exercise intensity; climatic conditions; the athlete's acclimatization; the athlete's physical conditioning; physiologic individual characteristics and the player's biomechanics. Performance is improved when players ingest not only water but also carbohydrate. Th...

  11. Mechanism of gypsum hydration

    Directory of Open Access Journals (Sweden)

    Pacheco, G.

    1991-06-01

    Full Text Available There is an hypothesis that the mechanism o f gypsum hydration and dehydration is performed through two simultaneous phenomena. In this study we try to clear up this phenomenon using chlorides as accelerators or a mixture of ethanol-methanol as retarders to carry out the gypsum setting. Natural Mexican gypsum samples and a hemihydrate prepared in the laboratory are used. The following analytical techniques are used: MO, DRX, DTA, TG and DTG. In agreement with the obtained results, it can be concluded: that colloid formation depends on the action of accelerators or retarders and the crystals are a consequence of the quantity of hemihydrate formed.

    En el mecanismo de hidratación y deshidratación del yeso existe la hipótesis de que éste se efectúa por dos fenómenos simultáneos. Este estudio intenta esclarecer estos fenómenos, empleando: cloruros como aceleradores o mezcla etanol-metanol como retardadores para efectuar el fraguado del yeso. Se emplean muestras de yeso de origen natural mexicano y hemihydrate preparado en laboratorio; se utilizan técnicas analíticas: MO, DRX, DTA, TG y DTG. De acuerdo a los resultados obtenidos se puede deducir: que la formación del coloide depende de la acción de los agentes aceleradores o retardadores y que los cristales son consecuencia de la cantidad de hemihidrato formado.

  12. Progress of Gas Hydrate Studies in China

    Institute of Scientific and Technical Information of China (English)

    樊栓狮; 汪集旸

    2006-01-01

    A brief overview is given on the gas hydrate-related research activities carried out by Chinese researchers in the past 15 years. The content involves: (1) Historical review. Introducing the gas hydrate research history in China; (2) Gas hydrate research groups in China. There are nearly 20 groups engaged in gas hydrate research now; (3) Present studies.Including fundamental studies, status of the exploration of natural gas hydrate resources in the South China Sea region, and development of hydrate-based new techniques; (4) Future development.

  13. Clinker mineral hydration at reduced relative humidities

    DEFF Research Database (Denmark)

    Jensen, Ole Mejlhede; Hansen, Per Freiesleben; Lachowski, Eric E.;

    1999-01-01

    Vapour phase hydration of purl cement clinker minerals at reduced relative humidities is described. This is relevant to modern high performance concrete that may self-desiccate during hydration and is also relevant to the quality of the cement during storage. Both the oretical considerations and...... experimental data are presented showing that C(3)A can hydrate at lower humidities than either C3S or C2S. It is suggested that the initiation of hydration during exposure to water vapour is nucleation controlled. When C(3)A hydrates at low humidity, the characteristic hydration product is C(3)AH(6...

  14. Hydration water in dynamics of a hydrated beta-lactoglobulin

    Science.gov (United States)

    Yoshida, K.; Yamaguchi, T.; Bellissent-Funel, M.-C.; Longeville, S.

    2007-02-01

    Incoherent spin-echo signals of a hydrated β-lactoglobulin protein were investigated, at 275 and 293 K. The intermediate scattering functions I(Q,t) were divided in two contributions from surface water and protein, respectively. On one hand, the dynamics of the surface water follows a KWW stretched exponential function (the exponent is ~0.5), on the other hand, that of the protein follows a single exponential. The present results are consistent with our previous results of hydrated C-phycocyanin combining elastic and quasielastic neutron scattering and by molecular dynamics simulation.

  15. Great Market Potential of Hydrazine Hydrate

    Institute of Scientific and Technical Information of China (English)

    Shi Yuying

    2007-01-01

    @@ Stable consumption growth worldwide Hydrazine hydrate is an organic chemical raw material with extensive applications. The world's capacity to produce hydrazine hydrate has reached more than 200 thousand t/atoday (based on 100% hydrazine content).

  16. 77 FR 40032 - Methane Hydrate Advisory Committee

    Science.gov (United States)

    2012-07-06

    ... Methane Hydrate Advisory Committee AGENCY: Office of Fossil Energy, Department of Energy. ACTION: Notice of open meeting. SUMMARY: This notice announces a meeting of the Methane Hydrate Advisory Committee.... SUPPLEMENTARY INFORMATION: Purpose of the Committee: The purpose of the Methane Hydrate Advisory Committee is...

  17. 75 FR 9886 - Methane Hydrate Advisory Committee

    Science.gov (United States)

    2010-03-04

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF ENERGY Methane... meeting. SUMMARY: This notice announces a meeting of the Methane Hydrate Advisory Committee. Federal... Methane Hydrate Advisory Committee is to provide advice on potential applications of methane hydrate...

  18. Physical properties of gas hydrates

    Energy Technology Data Exchange (ETDEWEB)

    Kliner, J.T.R.; Grozic, J.L.H. [Calgary Univ., AB (Canada)

    2003-07-01

    Gas hydrates are naturally occurring, solid crystalline compounds (clathrates) that encapsulate gas molecules inside the lattices of hydrogen bonded water molecules within a specific temperature-pressure stability zone. Estimates of the total quantity of available methane gas in natural occurring hydrates are based on twice the energy content of known conventional fossil fuels reservoirs. Accurate and reliable in-situ quantification techniques are essential in determining the economic viability of this potential energy yield, which is dependent upon several factors such as sensitivity of the temperature-pressure stability zone, sediment type, porosity, permeability, concentration/abundance of free gas, spatial distribution in pore spaces, specific cage occupancy, and the influence of inhibitors. Various techniques like acoustic P and S waves, time domain reflectometry, and electrical resistance have been used to analyze the quantity and spatial distribution of the gas hydrate samples. These techniques were reviewed and the results obtained in the course of gas hydrate research were presented. 34 refs., 8 figs.

  19. Mesoscale texture of cement hydrates.

    Science.gov (United States)

    Ioannidou, Katerina; Krakowiak, Konrad J; Bauchy, Mathieu; Hoover, Christian G; Masoero, Enrico; Yip, Sidney; Ulm, Franz-Josef; Levitz, Pierre; Pellenq, Roland J-M; Del Gado, Emanuela

    2016-02-23

    Strength and other mechanical properties of cement and concrete rely upon the formation of calcium-silicate-hydrates (C-S-H) during cement hydration. Controlling structure and properties of the C-S-H phase is a challenge, due to the complexity of this hydration product and of the mechanisms that drive its precipitation from the ionic solution upon dissolution of cement grains in water. Departing from traditional models mostly focused on length scales above the micrometer, recent research addressed the molecular structure of C-S-H. However, small-angle neutron scattering, electron-microscopy imaging, and nanoindentation experiments suggest that its mesoscale organization, extending over hundreds of nanometers, may be more important. Here we unveil the C-S-H mesoscale texture, a crucial step to connect the fundamental scales to the macroscale of engineering properties. We use simulations that combine information of the nanoscale building units of C-S-H and their effective interactions, obtained from atomistic simulations and experiments, into a statistical physics framework for aggregating nanoparticles. We compute small-angle scattering intensities, pore size distributions, specific surface area, local densities, indentation modulus, and hardness of the material, providing quantitative understanding of different experimental investigations. Our results provide insight into how the heterogeneities developed during the early stages of hydration persist in the structure of C-S-H and impact the mechanical performance of the hardened cement paste. Unraveling such links in cement hydrates can be groundbreaking and controlling them can be the key to smarter mix designs of cementitious materials. PMID:26858450

  20. Physical activity, hydration and health

    Directory of Open Access Journals (Sweden)

    Ascensión Marcos

    2014-06-01

    Full Text Available Since the beginning of mankind, man has sought ways to promote and preserve health as well as to prevent disease. Hydration, physical activity and exercise are key factors for enhancing human health. However, either a little dose of them or an excess can be harmful for health maintenance at any age. Water is an essential nutrient for human body and a major key to survival has been to prevent dehydration. However, there is still a general controversy regarding the necessary amount to drink water or other beverages to properly get an adequate level of hydration. In addition, up to now the tools used to measure hydration are controversial. To this end, there are several important groups of variables to take into account such as water balance, hydration biomarkers and total body water. A combination of methods will be the most preferred tool to find out any risk or situation of dehydration at any age range. On the other hand, physical activity and exercise are being demonstrated to promote health, avoiding or reducing health problems, vascular and inflammatory diseases and helping weight management. Therefore, physical activity is also being used as a pill within a therapy to promote health and reduce risk diseases, but as in the case of drugs, dose, intensity, frequency, duration and precautions have to be evaluated and taken into account in order to get the maximum effectiveness and success of a treatment. On the other hand, sedentariness is the opposite concept to physical activity that has been recently recognized as an important factor of lifestyle involved in the obesogenic environment and consequently in the risk of the non-communicable diseases. In view of the literature consulted and taking into account the expertise of the authors, in this review a Decalogue of global recommendations is included to achieve an adequate hydration and physical activity status to avoid overweight/obesity consequences.

  1. Seismic reflections associated with submarine gas hydrates

    Energy Technology Data Exchange (ETDEWEB)

    Andreassen, K.

    1995-12-31

    Gas hydrates are often suggested as a future energy resource. This doctoral thesis improves the understanding of the concentration and distribution of natural submarine gas hydrates. The presence of these hydrates are commonly inferred from strong bottom simulating reflection (BSR). To investigate the nature of BSR, this work uses seismic studies of hydrate-related BSRs at two different locations, one where gas hydrates are accepted to exist and interpreted to be very extensive (in the Beaufort Sea), the other with good velocity data and downhole logs available (offshore Oregon). To ascertain the presence of free gas under the BSR, prestack offset data must supplement near-vertical incidence seismic data. A tentative model for physical properties of sediments partially saturated with gas hydrate and free gas is presented. This model, together with drilling information and seismic data containing the BSR beneath the Oregon margin and the Beaufort Sea, made it possible to better understand when to apply the amplitude-versus-offset (AVO) method to constrain BSR gas hydrate and gas models. Distribution of natural gas hydrates offshore Norway and Svalbard is discussed and interpreted as reflections from the base of gas hydrate-bearing sediments, overlying sediments containing free gas. Gas hydrates inferred to exist at the Norwegian-Svalbard continental margin correlate well with Cenozoic depocenters, and the associated gas is assumed to be mainly biogenic. Parts of that margin have a high potential for natural gas hydrates of both biogenic and thermogenic origin. 235 refs., 86 figs., 4 tabs.

  2. Influence of fluorosurfactants on hydrate formation rates

    Energy Technology Data Exchange (ETDEWEB)

    Kim, C.U.; Jeong, K.E.; Chae, H.J.; Jeong, S.Y. [Korea Reasearch Inst. of Chemical Technology, Alternative Chemicals/Fuel Research Center, Yuseong-Gu, Daejon (Korea, Republic of)

    2008-07-01

    Gas hydrates, or clathrates, are ice-like solids that forms when natural gas is in contact with liquid water or ice under high pressure and low temperature. There is significant interest in studying the storage and transportation of gas in the form of hydrates. However, a critical problem impacting the industrial application of gas hydrates for storage and transportation of natural gas is the slow formation rate of natural gas hydrate. Researchers have previously reported on the promotion effect of some additives on gas hydrate formation and hydrate gas content. Fluorosurfactants are significantly superior to nonfluorinated surfactants in wetting action, as well as stability in harsh environments, both thermal and chemical. This paper discussed an experimental investigation into the effects of fluorosurfactants with different ionic types on the formation of methane hydrate. The surfactants used were FSN-100 of DuPont Zonyl as non-ionic surfactant and FC-143 of DuPont as anionic surfactant. The paper discussed the experimental apparatus for methane hydrate formation. It also discussed hydrate formation kinetics and the series of hydrate formation experiments that were conducted in the presence of fluorosurfactants. Last, the paper explored the results of the study. It was concluded that anionic fluorosurfactant of FC-143 had a better promoting effect on methane hydrate formation compared with nonionic surfactant of FSN-100. 8 refs., 2 tabs., 2 figs.

  3. Is the Surface of Gas Hydrates Dry?

    Directory of Open Access Journals (Sweden)

    Nobuo Maeda

    2015-06-01

    Full Text Available Adhesion (cohesion and agglomeration properties of gas hydrate particles have been a key to hydrate management in flow assurance in natural gas pipelines. Despite its importance, the relevant data in the area, such as the surface energy and the interfacial energy of gas hydrates with gas and/or water, are scarce; presumably due to the experimental difficulties involved in the measurements. Here we review what is known about the surface energy and the interfacial energy of gas hydrates to date. In particular, we ask a question as to whether pre-melting can occur on the surface of gas hydrates. Surface thermodynamic analyses show that pre-melting is favoured to occur on the surface of gas hydrates, however, not sufficient data are available to assess its thickness. The effects of the existence of pre-melting layers on the cohesion and friction forces between gas hydrate particles are also discussed.

  4. Handbook of gas hydrate properties and occurrence

    Energy Technology Data Exchange (ETDEWEB)

    Kuustraa, V.A.; Hammershaimb, E.C.

    1983-12-01

    This handbook provides data on the resource potential of naturally occurring hydrates, the properties that are needed to evaluate their recovery, and their production potential. The first two chapters give data on the naturally occurring hydrate potential by reviewing published resource estimates and the known and inferred occurrences. The third and fourth chapters review the physical and thermodynamic properties of hydrates, respectively. The thermodynamic properties of hydrates that are discussed include dissociation energies and a simplified method to calculate them; phase diagrams for simple and multi-component gases; the thermal conductivity; and the kinetics of hydrate dissociation. The final chapter evaluates the net energy balance of recovering hydrates and shows that a substantial positive energy balance can theoretically be achieved. The Appendices of the Handbook summarize physical and thermodynamic properties of gases, liquids and solids that can be used in designing and evaluating recovery processes of hydrates. 158 references, 67 figures, 47 tables.

  5. Well log characterization of natural gas hydrates

    Science.gov (United States)

    Collett, Timothy S.; Lee, Myung W.

    2011-01-01

    In the last 25 years we have seen significant advancements in the use of downhole well logging tools to acquire detailed information on the occurrence of gas hydrate in nature: From an early start of using wireline electrical resistivity and acoustic logs to identify gas hydrate occurrences in wells drilled in Arctic permafrost environments to today where wireline and advanced logging-while-drilling tools are routinely used to examine the petrophysical nature of gas hydrate reservoirs and the distribution and concentration of gas hydrates within various complex reservoir systems. The most established and well known use of downhole log data in gas hydrate research is the use of electrical resistivity and acoustic velocity data (both compressional- and shear-wave data) to make estimates of gas hydrate content (i.e., reservoir saturations) in various sediment types and geologic settings. New downhole logging tools designed to make directionally oriented acoustic and propagation resistivity log measurements have provided the data needed to analyze the acoustic and electrical anisotropic properties of both highly inter-bedded and fracture dominated gas hydrate reservoirs. Advancements in nuclear-magnetic-resonance (NMR) logging and wireline formation testing have also allowed for the characterization of gas hydrate at the pore scale. Integrated NMR and formation testing studies from northern Canada and Alaska have yielded valuable insight into how gas hydrates are physically distributed in sediments and the occurrence and nature of pore fluids (i.e., free-water along with clay and capillary bound water) in gas-hydrate-bearing reservoirs. Information on the distribution of gas hydrate at the pore scale has provided invaluable insight on the mechanisms controlling the formation and occurrence of gas hydrate in nature along with data on gas hydrate reservoir properties (i.e., permeabilities) needed to accurately predict gas production rates for various gas hydrate

  6. Pockmark formation and evolution in deep water Nigeria: Rapid hydrate growth versus slow hydrate dissolution

    Science.gov (United States)

    Sultan, N.; Bohrmann, G.; Ruffine, L.; Pape, T.; Riboulot, V.; Colliat, J.-L.; De Prunelé, A.; Dennielou, B.; Garziglia, S.; Himmler, T.; Marsset, T.; Peters, C. A.; Rabiu, A.; Wei, J.

    2014-04-01

    In previous works, it has been suggested that dissolution of gas hydrate can be responsible for pockmark formation and evolution in deep water Nigeria. It was shown that those pockmarks which are at different stages of maturation are characterized by a common internal architecture associated to gas hydrate dynamics. New results obtained by drilling into gas hydrate-bearing sediments with the MeBo seafloor drill rig in concert with geotechnical in situ measurements and pore water analyses indicate that pockmark formation and evolution in the study area are mainly controlled by rapid hydrate growth opposed to slow hydrate dissolution. On one hand, positive temperature anomalies, free gas trapped in shallow microfractures near the seafloor and coexistence of free gas and gas hydrate indicate rapid hydrate growth. On the other hand, slow hydrate dissolution is evident by low methane concentrations and almost constant sulfate values 2 m above the Gas Hydrate Occurrence Zone.

  7. Synthesis of hydrated lutetium carbonate

    Energy Technology Data Exchange (ETDEWEB)

    Song Liu [South China Univ. of Technology, Dept. of Applied Chemistry, Guangdong (China); Rong-jun Ma [Changsha Research Institute of Minig and Metallurgy, Hunan (China)

    1997-09-01

    Crystalline lutetium carbonate was synthesized for the corresponding chloride using ammonium bicarbonate as precipitant. The chemical analyses suggest that the synthesized lutetium carbonate is a hydrated basic carbonate or oxycarbonate. The X-ray powder diffraction data are presented. The IR data for the compound show the presence of two different carbonate groups. There is no stable intermediate carbonate in the process of thermal decomposition of the lutetium carbonate. (au) 15 refs.

  8. Well log evaluation of gas hydrate saturations

    Science.gov (United States)

    Collett, Timothy S.

    1998-01-01

    The amount of gas sequestered in gas hydrates is probably enormous, but estimates are highly speculative due to the lack of previous quantitative studies. Gas volumes that may be attributed to a gas hydrate accumulation within a given geologic setting are dependent on a number of reservoir parameters; one of which, gas-hydrate saturation, can be assessed with data obtained from downhole well logging devices. The primary objective of this study was to develop quantitative well-log evaluation techniques which will permit the calculation of gas-hydrate saturations in gas-hydrate-bearing sedimentary units. The `standard' and `quick look' Archie relations (resistivity log data) yielded accurate gas-hydrate and free-gas saturations within all of the gas hydrate accumulations assessed in the field verification phase of the study. Compressional wave acoustic log data have been used along with the Timur, modified Wood, and the Lee weighted average acoustic equations to calculate accurate gas-hydrate saturations in this study. The well log derived gas-hydrate saturations calculated in the field verification phase of this study, which range from as low as 2% to as high as 97%, confirm that gas hydrates represent a potentially important source of natural gas.

  9. Micelle Structure and Hydrophobic Hydration.

    Science.gov (United States)

    Long, Joshua A; Rankin, Blake M; Ben-Amotz, Dor

    2015-08-26

    Despite the ubiquity and utility of micelles self-assembled from aqueous surfactants, longstanding questions remain regarding their surface structure and interior hydration. Here we combine Raman spectroscopy with multivariate curve resolution (Raman-MCR) to probe the hydrophobic hydration of surfactants with various aliphatic chain lengths, and either anionic (carboxylate) or cationic (trimethylammonium) head groups, both below and above the critical micelle concentration. Our results reveal significant penetration of water into micelle interiors, well beyond the first few carbons adjacent to the headgroup. Moreover, the vibrational C-D frequency shifts of solubilized deuterated n-hexane confirm that it resides in a dry, oil-like environment (while the localization of solubilized benzene is sensitive to headgroup charge). Our findings imply that the hydrophobic core of a micelle is surrounded by a highly corrugated surface containing hydrated non-polar cavities whose depth increases with increasing surfactant chain length, thus bearing a greater resemblance to soluble proteins than previously recognized. PMID:26222042

  10. Gas hydrates: Technology status report

    Energy Technology Data Exchange (ETDEWEB)

    1987-01-01

    In 1983, the US Department of Energy (DOE) assumed the responsibility for expanding the knowledge base and for developing methods to recover gas from hydrates. These are ice-like mixtures of gas and water where gas molecules are trapped within a framework of water molecules. This research is part of the Unconventional Gas Recovery (UGR) program, a multidisciplinary effort that focuses on developing the technology to produce natural gas from resources that have been classified as unconventional because of their unique geologies and production mechanisms. Current work on gas hydrates emphasizes geological studies; characterization of the resource; and generic research, including modeling of reservoir conditions, production concepts, and predictive strategies for stimulated wells. Complementing this work is research on in situ detection of hydrates and field tests to verify extraction methods. Thus, current research will provide a comprehensive technology base from which estimates of reserve potential can be made, and from which industry can develop recovery strategies. 7 refs., 3 figs., 6 tabs.

  11. Study of Formation Mechanisms of Gas Hydrate

    Science.gov (United States)

    Yang, Jia-Sheng; Wu, Cheng-Yueh; Hsieh, Bieng-Zih

    2015-04-01

    Gas hydrates, which had been found in subsurface geological environments of deep-sea sediments and permafrost regions, are solid crystalline compounds of gas molecules and water. The estimated energy resources of hydrates are at least twice of that of the conventional fossil fuel in the world. Gas hydrates have a great opportunity to become a dominating future energy. In the past years, many laboratory experiments had been conducted to study chemical and thermodynamic characteristics of gas hydrates in order to investigate the formation and dissociation mechanisms of hydrates. However, it is difficult to observe the formation and dissociation of hydrates in a porous media from a physical experiment directly. The purpose of this study was to model the dynamic formation mechanisms of gas hydrate in porous media by reservoir simulation. Two models were designed for this study: 1) a closed-system static model with separated gas and water zones; this model was a hydrate equilibrium model to investigate the behavior of the formation of hydrates near the initial gas-water contact; and 2) an open-system dynamic model with a continuous bottom-up gas flow; this model simulated the behavior of gas migration and studied the formation of hydrates from flowed gas and static formation water in porous media. A phase behavior module was developed in this study for reservoir simulator to model the pressure-volume-temperature (PVT) behavior of hydrates. The thermodynamic equilibriums and chemical reactions were coupled with the phase behavior module to have functions modelling the formation and dissociation of hydrates from/to water and gas. The simulation models used in this study were validated from the code-comparison project proposed by the NETL. According to the modelling results of the closed-system static model, we found that predominated location for the formation of hydrates was below the gas-water contact (or at the top of water zone). The maximum hydrate saturation

  12. Development of Alaskan gas hydrate resources

    Energy Technology Data Exchange (ETDEWEB)

    Kamath, V.A.; Sharma, G.D.; Patil, S.L.

    1991-06-01

    The research undertaken in this project pertains to study of various techniques for production of natural gas from Alaskan gas hydrates such as, depressurization, injection of hot water, steam, brine, methanol and ethylene glycol solutions through experimental investigation of decomposition characteristics of hydrate cores. An experimental study has been conducted to measure the effective gas permeability changes as hydrates form in the sandpack and the results have been used to determine the reduction in the effective gas permeability of the sandpack as a function of hydrate saturation. A user friendly, interactive, menu-driven, numerical difference simulator has been developed to model the dissociation of natural gas hydrates in porous media with variable thermal properties. A numerical, finite element simulator has been developed to model the dissociation of hydrates during hot water injection process.

  13. Fundamentals and applications of gas hydrates.

    Science.gov (United States)

    Koh, Carolyn A; Sloan, E Dendy; Sum, Amadeu K; Wu, David T

    2011-01-01

    Fundamental understanding of gas hydrate formation and decomposition processes is critical in many energy and environmental areas and has special importance in flow assurance for the oil and gas industry. These areas represent the core of gas hydrate applications, which, albeit widely studied, are still developing as growing fields of research. Discovering the molecular pathways and chemical and physical concepts underlying gas hydrate formation potentially can lead us beyond flowline blockage prevention strategies toward advancing new technological solutions for fuel storage and transportation, safely producing a new energy resource from natural deposits of gas hydrates in oceanic and arctic sediments, and potentially facilitating effective desalination of seawater. The state of the art in gas hydrate research is leading us to new understanding of formation and dissociation phenomena that focuses on measurement and modeling of time-dependent properties of gas hydrates on the basis of their well-established thermodynamic properties. PMID:22432618

  14. SEISMIC STUDIES OF MARINE GAS HYDRATES

    Institute of Scientific and Technical Information of China (English)

    SONG Haibin

    2003-01-01

    We give a brief introduction of developments of seismic methods in the studies of marine gas hydrates. Then we give an example of seismic data processing for BSRs in western Nankai accretionary prism, a typical gas hydrate distribution region. Seismic data processing is proved to be important to obtain better images of BSRs distribution. Studies of velocity structure of hydrated sediments are useful for better understanding the distribution of gas hydrates. Using full waveform inversion, we successfully derived high-resolution velocity model of a double BSR in eastern Nankai Trough area. Recent survey and research show that gas hydrates occur in the marine sediments of the South China Sea and East China Sea.But we would like to say seismic researches on gas hydrate in China are very preliminary.

  15. Geomechanical Modeling of Gas Hydrate Bearing Sediments

    Science.gov (United States)

    Sanchez, M. J.; Gai, X., Sr.

    2015-12-01

    This contribution focuses on an advance geomechanical model for methane hydrate-bearing soils based on concepts of elasto-plasticity for strain hardening/softening soils and incorporates bonding and damage effects. The core of the proposed model includes: a hierarchical single surface critical state framework, sub-loading concepts for modeling the plastic strains generally observed inside the yield surface and a hydrate enhancement factor to account for the cementing effects provided by the presence of hydrates in sediments. The proposed framework has been validated against recently published experiments involving both, synthetic and natural hydrate soils, as well as different sediments types (i.e., different hydrate saturations, and different hydrates morphologies) and confinement conditions. The performance of the model in these different case studies was very satisfactory.

  16. Terahertz Time Domain Spectroscopy for Structure-II Gas Hydrates

    DEFF Research Database (Denmark)

    Takeya, Kei; Zhang, Caihong; Kawayama, Iwao;

    2009-01-01

    For the nondestructive inspection of gas hydrates, terahertz (THz) time-domain spectroscopy (TDS) was applied to tetrahydrofuran (THF) hydrate and propane hydrate. The absorption of propane hydrate monotonically increases with frequency, similar to the case of ice, while THF hydrate has a charact...

  17. Desalination utilizing clathrate hydrates (LDRD final report).

    Energy Technology Data Exchange (ETDEWEB)

    Simmons, Blake Alexander; Bradshaw, Robert W.; Dedrick, Daniel E.; Cygan, Randall Timothy (Sandia National Laboratories, Albuquerque, NM); Greathouse, Jeffery A. (Sandia National Laboratories, Albuquerque, NM); Majzoub, Eric H. (University of Missouri, Columbia, MO)

    2008-01-01

    Advances are reported in several aspects of clathrate hydrate desalination fundamentals necessary to develop an economical means to produce municipal quantities of potable water from seawater or brackish feedstock. These aspects include the following, (1) advances in defining the most promising systems design based on new types of hydrate guest molecules, (2) selection of optimal multi-phase reactors and separation arrangements, and, (3) applicability of an inert heat exchange fluid to moderate hydrate growth, control the morphology of the solid hydrate material formed, and facilitate separation of hydrate solids from concentrated brine. The rate of R141b hydrate formation was determined and found to depend only on the degree of supercooling. The rate of R141b hydrate formation in the presence of a heat exchange fluid depended on the degree of supercooling according to the same rate equation as pure R141b with secondary dependence on salinity. Experiments demonstrated that a perfluorocarbon heat exchange fluid assisted separation of R141b hydrates from brine. Preliminary experiments using the guest species, difluoromethane, showed that hydrate formation rates were substantial at temperatures up to at least 12 C and demonstrated partial separation of water from brine. We present a detailed molecular picture of the structure and dynamics of R141b guest molecules within water cages, obtained from ab initio calculations, molecular dynamics simulations, and Raman spectroscopy. Density functional theory calculations were used to provide an energetic and molecular orbital description of R141b stability in both large and small cages in a structure II hydrate. Additionally, the hydrate of an isomer, 1,2-dichloro-1-fluoroethane, does not form at ambient conditions because of extensive overlap of electron density between guest and host. Classical molecular dynamics simulations and laboratory trials support the results for the isomer hydrate. Molecular dynamics simulations

  18. Separation of water through gas hydrate formation

    DEFF Research Database (Denmark)

    Boch Andersen, Torben; Thomsen, Kaj

    2009-01-01

    Gas hydrate is normally recognized as a troublemaker in the oil and gas industry. However, gas hydrate has some interesting possibilities when used in connection with separation of water. Nordic Sugar has investigated the possibility of using gas hydrates for concentration of sugar juice. The goal...... of the project was to formulate an alternative separation concept, which can replace the traditional water evaporation process in the sugar production. Work with the separation concept showed that gas hydrates can be used for water separation. The process is not suitable for sugar production because of large...

  19. Observations related to tetrahydrofuran and methane hydrates for laboratory studies of hydrate-bearing sediments

    Science.gov (United States)

    Lee, J.Y.; Yun, T.S.; Santamarina, J.C.; Ruppel, C.

    2007-01-01

    The interaction among water molecules, guest gas molecules, salts, and mineral particles determines the nucleation and growth behavior of gas hydrates in natural sediments. Hydrate of tetrahydrofuran (THF) has long been used for laboratory studies of gas hydrate-bearing sediments to provide close control on hydrate concentrations and to overcome the long formation history of methane hydrate from aqueous phase methane in sediments. Yet differences in the polarizability of THF (polar molecule) compared to methane (nonpolar molecule) raise questions about the suitability of THF as a proxy for methane in the study of hydrate-bearing sediments. From existing data and simple macroscale experiments, we show that despite its polar nature, THF's large molecular size results in low permittivity, prevents it from dissolving precipitated salts, and hinders the solvation of ions on dry mineral surfaces. In addition, the interfacial tension between water and THF hydrate is similar to that between water and methane hydrate. The processes that researchers choose for forming hydrate in sediments in laboratory settings (e.g., from gas, liquid, or ice) and the pore-scale distribution of the hydrate that is produced by each of these processes likely have a more pronounced effect on the measured macroscale properties of hydrate-bearing sediments than do differences between THF and methane hydrates themselves.

  20. Hydration in soccer: a review

    Directory of Open Access Journals (Sweden)

    Monteiro Cristiano Ralo

    2003-01-01

    Full Text Available Hydration should be considered before, during and after the exercise. This review intends to approach the main points of hydration process in soccer. The replacement of fluids during exercise is proportional to some factors, such as: exercise intensity; climatic conditions; the athlete's acclimatization; the athlete's physical conditioning; physiologic individual characteristics and the player's biomechanics. Performance is improved when players ingest not only water but also carbohydrate. The rates that carbohydrate and water are absorbed by the organism are limited by the rates of gastric emptying and intestinal absorption. The composition of drinks offered to the players should be influenced by the relative importance of the need of supplying carbohydrates or water; it should be remembered that the depletion of carbohydrate can result in fatigue and decrease of performance, but it is not usually a life-threatening condition. The addition of carbohydrate in these drinks increases the concentrations of blood glucose, increases the use of external fuel through the increase of the glucose oxidation in the muscles and it spares muscle glycogen. So, the ingestion of carbohydrate before and during the exercise can delay the emergence of fatigue and increase the players' performance. Several tactics can be used to avoid dehydration, like hyperhydration before exercise and player's acclimatization. The ideal situation to restore the player's fluid losses is between the sessions of exercises. Since soccer is a sport with quite peculiar characteristics related to hydration, the players should be concerned and educated about the importance of fluid ingestion before, during and after the exercise.

  1. Hydration behaviour of polyhydroxylated fullerenes

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez-Zavala, J G [Departamento de Ciencias Exactas y Tecnologicas, Centro Universitario de Los Lagos, Universidad de Guadalajara, Enrique Diaz de Leon S/N, 47460 Jalisco (Mexico); Barajas-Barraza, R E [Departamento de Matematicas y Fisica, Instituto Tecnologico y de Estudios Superiores de Occidente, Periferico Sur, Manuel Gomez MorIn No 8585, 45604 Jalisco (Mexico); Padilla-Osuna, I; Guirado-Lopez, R A, E-mail: jgrz@culagos.udg.mx, E-mail: ebarajas@iteso.mx, E-mail: ismael@ifisica.uaslp.mx, E-mail: guirado@ifisica.uaslp.mx [Instituto de Fisica ' Manuel Sandoval Vallarta' , Universidad Autonoma de San Luis Potosi, Alvaro Obregon 64, 78000 San Luis Potosi (Mexico)

    2011-10-28

    We have performed semi-empirical as well as density functional theory calculations in order to analyse the hydration properties of both bare C{sub 60} and highly hydroxylated C{sub 60}(OH){sub 26} fullerenes. In all of our calculations, a total of 42 and 98 water molecules are always surrounding our here-considered carbon nanostructures. We found different wetting properties as a function of the chemical composition and structure of the OH-molecular over-layer covering the fullerene surface. In the case of bare C{sub 60}, water adsorption reveals that the H{sub 2}O species are not uniformly arranged around the carbon network but rather forms water droplets of different sizes, clearly revealing the hydrophobic nature of the C{sub 60} structure. In contrast, in the polyhydroxylated C{sub 60}(OH){sub 26} fullerenes, the degree of wetting is strongly influenced by the precise location of the hydroxyl groups. We found that different adsorbed configurations for the OH-molecular coating can lead to the formation of partially hydrated or completely covered C{sub 60}(OH){sub 26} compounds, a result that could be used to synthesize fullerene materials with different degrees of wettability. By comparing the relative stability of our hydroxylated structures in both bare and hydrated conditions we obtain that the energy ordering of the C{sub 60}(OH){sub 26} isomers can change in the presence of water. The radial distribution function of our hydrated fullerenes reveals that water near these kinds of surfaces is densely packed. In fact, by counting the number of H{sub 2}O molecules which are adsorbed, by means of hydrogen bonds, to the surface of our more stable C{sub 60}(OH){sub 26} isomer, we found that it varies in the range of 5-10, in good agreement with experiments. Finally, by comparing the calculated optical absorption spectra of various C{sub 60}(OH){sub 26} structures in the presence and absence of water molecules, we note that only slight variations in the position and

  2. Protein dynamics: hydration and cavities

    Directory of Open Access Journals (Sweden)

    Heremans K.

    2005-01-01

    Full Text Available The temperature-pressure behavior of proteins seems to be unique among the biological macromolecules. Thermodynamic as well as kinetic data show the typical elliptical stability diagram. This may be extended by assuming that the unfolded state gives rise to volume and enthalpy-driven liquid-liquid transitions. A molecular interpretation follows from the temperature and the pressure dependence of the hydration and cavities. We suggest that positron annihilation spectroscopy can provide additional quantitative evidence for the contributions of cavities to the dynamics of proteins. Only mature amyloid fibrils that form from unfolded proteins are very resistant to pressure treatment.

  3. Methods of gas hydrate concentration estimation with field examples

    Digital Repository Service at National Institute of Oceanography (India)

    Kumar, D.; Dash, R.; Dewangan, P.

    important factors being the background property value in the absence of gas hydrate, and the modeling relationship between the physical property and gas hydrate saturation. a simple work-flow for hydrate saturation estimation from seismic velocity in a...

  4. Formation rate of natural gas hydrate

    Energy Technology Data Exchange (ETDEWEB)

    Mork, Marit

    2002-07-01

    The rate of methane hydrate and natural gas hydrate formation was measured in a 9.5 litre stirred tank reactor of standard design. The experiments were performed to better understand the performance and scale-up of a reactor for continuous production of natural gas hydrates. The hydrate formation rate was measured at steady-state conditions at pressures between 70 and 90 bar and temperatures between 7 and 15 deg C. Between 44 and 56 % of the gas continuously supplied to the reactor was converted to hydrate. The experimental results show that the rate of hydrate formation is strongly influenced by gas injection rate and pressure. The effect of stirring rate is less significant and subcooling has no observable effect on the formation rate. Hydrate crystal concentration and gas composition do not influence the hydrate formation rate. Observations of produced hydrate crystals indicate that the crystals are elongated, about 5 micron in diameter and 10 micron long. Analysis of the results shows that the rate of hydrate formation is dominated by gas-liquid mass transfer. A mass transfer model, the bubble-to-crystal model, was developed for the hydrate formation rate in a continuous stirred tank reactor, given in terms of concentration driving force and an overall mass transfer coefficient. The driving force is the difference between the gas concentration at the gas-liquid interface and at the hydrate crystal surface. These concentrations correspond to the solubility of gas in water at experimental temperature and pressure and the solubility of gas at hydrate equilibrium temperature and experimental pressure, respectively. The overall mass transfer coefficient is expressed in terms of superficial gas velocity and impeller power consumption, parameters commonly used in study of stirred tank reactors. Experiments and modeling show that the stirred tank reactor has a considerable potential for increased production capacity. However, at higher hydrate production rates the

  5. Gas hydrate inhibition of drilling fluid additives

    Energy Technology Data Exchange (ETDEWEB)

    Xiaolan, L.; Baojiang, S.; Shaoran, R. [China Univ. of Petroleum, Dongying (China). Inst. of Petroleum Engineering

    2008-07-01

    Gas hydrates that form during offshore well drilling can have adverse impacts on well operational safety. The hydrates typically form in the risers and the annulus between the casing and the drillstring, and can stop the circulation of drilling fluids. In this study, experiments were conducted to measure the effect of drilling fluid additives on hydrate inhibition. Polyalcohols, well-stability control agents, lubricating agents, and polymeric materials were investigated in a stirred tank reactor at temperatures ranging from -10 degree C to 60 degrees C. Pressure, temperature, and torque were used to detect onset points of hydrate formation and dissociation. The inhibitive effect of the additives on hydrate formation was quantified. Phase boundary shifts were measured in terms of temperature difference or sub-cooling gained when chemicals were added to pure water. Results showed that the multiple hydroxyl groups in polyalcohol chemicals significantly inhibited hydrate formation. Polymeric and polyacrylamide materials had only a small impact on hydrate formation, while sulfonated methyl tannins were found to increase hydrate formation. 6 refs., 1 tab., 4 figs.

  6. 78 FR 37536 - Methane Hydrate Advisory Committee

    Science.gov (United States)

    2013-06-21

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF ENERGY Methane... meeting. SUMMARY: This notice announces a meeting of the Methane Hydrate Advisory Committee. The Federal... of the Methane Hydrate Advisory Committee is to provide advice on potential applications of...

  7. 76 FR 59667 - Methane Hydrate Advisory Committee

    Science.gov (United States)

    2011-09-27

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF ENERGY Methane... Meeting. SUMMARY: This notice announces a meeting of the Methane Hydrate Advisory Committee. Federal... of the Committee: The purpose of the Methane Hydrate Advisory Committee is to provide advice...

  8. 78 FR 26337 - Methane Hydrate Advisory Committee

    Science.gov (United States)

    2013-05-06

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF ENERGY Methane... Meeting. SUMMARY: This notice announces a meeting of the Methane Hydrate Advisory Committee. The Federal... of the Methane Hydrate Advisory Committee is to provide advice on potential applications of...

  9. A new geotechnical gas hydrates research laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Grozic, J.L.H. [Calgary Univ., AB (Canada)

    2003-07-01

    Gas hydrates encapsulate natural gas molecules in a very compact form, as ice-like compounds composed of water molecules. Permafrost environments and offshore areas contain vast quantities of gas hydrates within soil and rock. This paper describes the role played by gas hydrates in submarine slope instability, their potential as a sustainable energy source, and their effects on global climate change. A new state-of-the-art laboratory located at the University of Calgary, which was developed to study the geomechanical behaviour of gas hydrate-sediment mixtures, was also presented. A specialized high pressure low temperature triaxial apparatus capable of performing a suite of tests on gas hydrate-sediment mixtures is housed in this laboratory. Extensive renovations were required in order to enable the use of methane gas to simulate natural hydrate formation conditions. The laboratory is specifically designed to examine the properties and behaviour of reconstituted gas hydrate-sediment mixtures and natural gas hydrate core samples. 26 refs., 9 figs.

  10. Raman Spectroscopic Studies of Methane Gas Hydrates

    DEFF Research Database (Denmark)

    Hansen, Susanne Brunsgaard; Berg, Rolf W.

    2009-01-01

    A brief review of the Raman spectroscopic studies of methane gas hydrates is given, supported by some new measurements done in our laboratory.......A brief review of the Raman spectroscopic studies of methane gas hydrates is given, supported by some new measurements done in our laboratory....

  11. Clinker mineral hydration at reduced relative humidities

    DEFF Research Database (Denmark)

    Jensen, Ole Mejlhede

    1998-01-01

    This report deals with gas phase hydration of pure cement clinker minerals at reduced relative humidities. This is an important subject in relation to modern high performance concrete which may self-desiccate during hydration. In addition the subject has relevance to storage stability where...

  12. METHANE HYDRATE PRODUCTION FROM ALASKAN PERMAFROST

    Energy Technology Data Exchange (ETDEWEB)

    Donn McGuire; Steve Runyon; Richard Sigal; Bill Liddell; Thomas Williams; George Moridis

    2005-02-01

    Natural-gas hydrates have been encountered beneath the permafrost and considered a nuisance by the oil and gas industry for years. Engineers working in Russia, Canada and the USA have documented numerous drilling problems, including kicks and uncontrolled gas releases, in arctic regions. Information has been generated in laboratory studies pertaining to the extent, volume, chemistry and phase behavior of gas hydrates. Scientists studying hydrate potential agree that the potential is great--on the North Slope of Alaska alone, it has been estimated at 590 TCF. However, little information has been obtained on physical samples taken from actual rock containing hydrates. This gas-hydrate project is in the final stages of a cost-shared partnership between Maurer Technology, Noble Corporation, Anadarko Petroleum, and the U.S. Department of Energy's Methane Hydrate R&D program. The purpose of the project is to build on previous and ongoing R&D in the area of onshore hydrate deposition to identify, quantify and predict production potential for hydrates located on the North Slope of Alaska. Hot Ice No. 1 was planned to test the Ugnu and West Sak sequences for gas hydrates and a concomitant free gas accumulation on Anadarko's 100% working interest acreage in section 30 of Township 9N, Range 8E of the Harrison Bay quadrangle of the North Slope of Alaska. The Ugnu and West Sak intervals are favorably positioned in the hydrate-stability zone over an area extending from Anadarko's acreage westward to the vicinity of the aforementioned gas-hydrate occurrences. This suggests that a large, north-to-south trending gas-hydrate accumulation may exist in that area. The presence of gas shows in the Ugnu and West Sak reservoirs in wells situated eastward and down dip of the Hot Ice location indicate that a free-gas accumulation may be trapped by gas hydrates. The Hot Ice No. 1 well was designed to core from the surface to the base of the West Sak interval using the

  13. Hydrate plug decomposition: Measurements and modeling

    Energy Technology Data Exchange (ETDEWEB)

    Yousif, M.H.; Dunayevsky, V.A.

    1995-12-31

    Depressurization (venting) is almost the only option available to remove hydrate blockages from subsea natural gas or gas condensate pipelines. This process is normally applied with little or no accurate information about the plug location, size or composition. Hydrate decomposition by depressurization is a heat and mass transfer dependent process. Quantifying this dependency is necessary to perform an optimum plug removal scheme. In this paper, a moving boundary mathematical model is developed to predict the decomposition rate of a hydrate plug under various depressurization scenarios. The model was validated experimentally by measuring the rate of decomposition of hydrate plugs in a 2 inch internal diameter, 38.5 inch long pipe. The motion of the hydrate plug/gas interface is tracked by 16 pairs of infrared light transmitters and receivers diametrically positioned across the pipe.

  14. METHANE HYDRATE PRODUCTION FROM ALASKAN PERMAFROST

    Energy Technology Data Exchange (ETDEWEB)

    Thomas E. Williams; Keith Millheim; Buddy King

    2004-07-01

    Natural-gas hydrates have been encountered beneath the permafrost and considered a nuisance by the oil and gas industry for years. Engineers working in Russia, Canada and the USA have documented numerous drilling problems, including kicks and uncontrolled gas releases, in arctic regions. Information has been generated in laboratory studies pertaining to the extent, volume, chemistry and phase behavior of gas hydrates. Scientists studying hydrate potential agree that the potential is great--on the North Slope of Alaska alone, it has been estimated at 590 TCF. However, little information has been obtained on physical samples taken from actual rock containing hydrates. This gas-hydrate project is in the final stages of a cost shared partnership between Maurer Technology, Noble Corporation, Anadarko Petroleum, and the U.S. Department of Energy's Methane Hydrate R&D program. The purpose of the project is to build on previous and ongoing R&D in the area of onshore hydrate deposition to identify, quantify and predict production potential for hydrates located on the North Slope of Alaska. The work scope drilled and cored a well The HOT ICE No.1 on Anadarko leases beginning in FY 2003 and completed in 2004. An on-site core analysis laboratory was built and utilized for determining the physical characteristics of the hydrates and surrounding rock. The well was drilled from a new Anadarko Arctic Platform that has a minimal footprint and environmental impact. The final efforts of the project are to correlate geology, geophysics, logs, and drilling and production data and provide this information to scientists developing reservoir models. No gas hydrates were encountered in this well; however, a wealth of information was generated and is contained in this report.

  15. METHANE HYDRATE PRODUCTION FROM ALASKAN PERMAFROST

    Energy Technology Data Exchange (ETDEWEB)

    Thomas E. Williams; Keith Millheim; Buddy King

    2004-06-01

    Natural-gas hydrates have been encountered beneath the permafrost and considered a nuisance by the oil and gas industry for years. Engineers working in Russia, Canada and the USA have documented numerous drilling problems, including kicks and uncontrolled gas releases, in arctic regions. Information has been generated in laboratory studies pertaining to the extent, volume, chemistry and phase behavior of gas hydrates. Scientists studying hydrate potential agree that the potential is great--on the North Slope of Alaska alone, it has been estimated at 590 TCF. However, little information has been obtained on physical samples taken from actual rock containing hydrates. This gas-hydrate project is in the final stages of a cost shared partnership between Maurer Technology, Noble Corporation, Anadarko Petroleum, and the U.S. Department of Energy's Methane Hydrate R&D program. The purpose of the project is to build on previous and ongoing R&D in the area of onshore hydrate deposition to identify, quantify and predict production potential for hydrates located on the North Slope of Alaska. The work scope drilled and cored a well The HOT ICE No.1 on Anadarko leases beginning in FY 2003 and completed in 2004. An on-site core analysis laboratory was built and utilized for determining the physical characteristics of the hydrates and surrounding rock. The well was drilled from a new Anadarko Arctic Platform that has a minimal footprint and environmental impact. The final efforts of the project are to correlate geology, geophysics, logs, and drilling and production data and provide this information to scientists developing reservoir models. No gas hydrates were encountered in this well; however, a wealth of information was generated and is contained in this report.

  16. METHANE HYDRATE PRODUCTION FROM ALASKAN PERMAFROST

    Energy Technology Data Exchange (ETDEWEB)

    Thomas E. Williams; Keith Millheim; Bill Liddell

    2005-03-01

    Natural-gas hydrates have been encountered beneath the permafrost and considered a nuisance by the oil and gas industry for years. Oil-field engineers working in Russia, Canada and the USA have documented numerous drilling problems, including kicks and uncontrolled gas releases, in Arctic regions. Information has been generated in laboratory studies pertaining to the extent, volume, chemistry and phase behavior of gas hydrates. Scientists studying hydrates agree that the potential is great--on the North Slope of Alaska alone, it has been estimated at 590 TCF. However, little information has been obtained on physical samples taken from actual rock containing hydrates. This gas-hydrate project is a cost-shared partnership between Maurer Technology, Anadarko Petroleum, Noble Corporation, and the U.S. Department of Energy's Methane Hydrate R&D program. The purpose of the project is to build on previous and ongoing R&D in the area of onshore hydrate deposition to help identify, quantify and predict production potential for hydrates located on the North Slope of Alaska. As part of the project work scope, team members drilled and cored the HOT ICE No. 1 on Anadarko leases beginning in January 2003 and completed in March 2004. Due to scheduling constraints imposed by the Arctic drilling season, operations at the site were suspended between April 21, 2003 and January 30, 2004. An on-site core analysis laboratory was designed, constructed and used for determining physical characteristics of frozen core immediately after it was retrieved from the well. The well was drilled from a new and innovative Anadarko Arctic Platform that has a greatly reduced footprint and environmental impact. Final efforts of the project were to correlate geology, geophysics, logs, and drilling and production data and provide this information to scientists for future hydrate operations. Unfortunately, no gas hydrates were encountered in this well; however, a wealth of information was generated

  17. Overview on Hydrate Coring, Handling and Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Jon Burger; Deepak Gupta; Patrick Jacobs; John Shillinglaw

    2003-06-30

    Gas hydrates are crystalline, ice-like compounds of gas and water molecules that are formed under certain thermodynamic conditions. Hydrate deposits occur naturally within ocean sediments just below the sea floor at temperatures and pressures existing below about 500 meters water depth. Gas hydrate is also stable in conjunction with the permafrost in the Arctic. Most marine gas hydrate is formed of microbially generated gas. It binds huge amounts of methane into the sediments. Worldwide, gas hydrate is estimated to hold about 1016 kg of organic carbon in the form of methane (Kvenvolden et al., 1993). Gas hydrate is one of the fossil fuel resources that is yet untapped, but may play a major role in meeting the energy challenge of this century. In June 2002, Westport Technology Center was requested by the Department of Energy (DOE) to prepare a ''Best Practices Manual on Gas Hydrate Coring, Handling and Analysis'' under Award No. DE-FC26-02NT41327. The scope of the task was specifically targeted for coring sediments with hydrates in Alaska, the Gulf of Mexico (GOM) and from the present Ocean Drilling Program (ODP) drillship. The specific subjects under this scope were defined in 3 stages as follows: Stage 1: Collect information on coring sediments with hydrates, core handling, core preservation, sample transportation, analysis of the core, and long term preservation. Stage 2: Provide copies of the first draft to a list of experts and stakeholders designated by DOE. Stage 3: Produce a second draft of the manual with benefit of input from external review for delivery. The manual provides an overview of existing information available in the published literature and reports on coring, analysis, preservation and transport of gas hydrates for laboratory analysis as of June 2003. The manual was delivered as draft version 3 to the DOE Project Manager for distribution in July 2003. This Final Report is provided for records purposes.

  18. Methane Recovery from Hydrate-bearing Sediments

    Energy Technology Data Exchange (ETDEWEB)

    J. Carlos Santamarina; Costas Tsouris

    2011-04-30

    Gas hydrates are crystalline compounds made of gas and water molecules. Methane hydrates are found in marine sediments and permafrost regions; extensive amounts of methane are trapped in the form of hydrates. Methane hydrate can be an energy resource, contribute to global warming, or cause seafloor instability. This study placed emphasis on gas recovery from hydrate bearing sediments and related phenomena. The unique behavior of hydrate-bearing sediments required the development of special research tools, including new numerical algorithms (tube- and pore-network models) and experimental devices (high pressure chambers and micromodels). Therefore, the research methodology combined experimental studies, particle-scale numerical simulations, and macro-scale analyses of coupled processes. Research conducted as part of this project started with hydrate formation in sediment pores and extended to production methods and emergent phenomena. In particular, the scope of the work addressed: (1) hydrate formation and growth in pores, the assessment of formation rate, tensile/adhesive strength and their impact on sediment-scale properties, including volume change during hydrate formation and dissociation; (2) the effect of physical properties such as gas solubility, salinity, pore size, and mixed gas conditions on hydrate formation and dissociation, and it implications such as oscillatory transient hydrate formation, dissolution within the hydrate stability field, initial hydrate lens formation, and phase boundary changes in real field situations; (3) fluid conductivity in relation to pore size distribution and spatial correlation and the emergence of phenomena such as flow focusing; (4) mixed fluid flow, with special emphasis on differences between invading gas and nucleating gas, implications on relative gas conductivity for reservoir simulations, and gas recovery efficiency; (5) identification of advantages and limitations in different gas production strategies with

  19. Clathrate hydrate tuning for technological purposes

    Science.gov (United States)

    di Profio, Pietro; Germani, Raimondo; Savelli, Gianfranco

    2010-05-01

    Gas hydrates are being increasingly considered as convenient media for gas storage and transportation as the knowledge of their properties increases, in particular as relates to methane and hydrogen. Clathrate hydrates may also represent a feasible sequestration technology for carbon dioxide, due to a well defined P/T range of stability, and several research programs are addressing this possibility. Though the understanding of the molecular structure and supramolecular interactions which are responsible of most properties of hydrates have been elucitated in recent years, the underlying theoretical physico-chemical framework is still poor, especially as relates to the role of "conditioners" (inhibitors and promoters) from the molecular/supramolecular point of view. In the present communication we show some results from our research approach which is mainly focused on the supramolecular properties of clathrate hydrate systems - and their conditioners - as a way to get access to a controlled modulation of the formation, dissociation and stabilization of gas hydrates. In particular, this communication will deal with: (a) a novel, compact apparatus for studying the main parameters of formation and dissociation of gas hydrates in a one-pot experiment, which can be easily and rapidly carried out on board of a drilling ship;[1] (b) the effects of amphiphile molecules (surfactants) as inhibitors or promoters of gas hydrate formation;[2] (c) a novel nanotechnology for a reliable and quick production of hydrogen hydrates, and its application to fuel cells;[3,4] and (d) the development of a clathrate hydrate tecnology for the sequestration and geological storage of man-made CO2, possibly with concomitant recovery of natural gas from NG hydrate fields. Furthermore, the feasibility of catalyzing the reduction of carbon dioxide to energy-rich species by hydrates is being investigated. [1] Di Profio, P., Germani, R., Savelli, G., International Patent Application PCT/IT2006

  20. Mass fractionation of noble gases in synthetic methane hydrate: Implications for naturally occurring gas hydrate dissociation

    Science.gov (United States)

    Hunt, Andrew G.; Stern, Laura; Pohlman, John W.; Ruppel, Carolyn; Moscati, Richard J.; Landis, Gary P.

    2013-01-01

    As a consequence of contemporary or longer term (since 15 ka) climate warming, gas hydrates in some settings may presently be dissociating and releasing methane and other gases to the ocean-atmosphere system. A key challenge in assessing the impact of dissociating gas hydrates on global atmospheric methane is the lack of a technique able to distinguish between methane recently released from gas hydrates and methane emitted from leaky thermogenic reservoirs, shallow sediments (some newly thawed), coal beds, and other sources. Carbon and deuterium stable isotopic fractionation during methane formation provides a first-order constraint on the processes (microbial or thermogenic) of methane generation. However, because gas hydrate formation and dissociation do not cause significant isotopic fractionation, a stable isotope-based hydrate-source determination is not possible. Here, we investigate patterns of mass-dependent noble gas fractionation within the gas hydrate lattice to fingerprint methane released from gas hydrates. Starting with synthetic gas hydrate formed under laboratory conditions, we document complex noble gas fractionation patterns in the gases liberated during dissociation and explore the effects of aging and storage (e.g., in liquid nitrogen), as well as sampling and preservation procedures. The laboratory results confirm a unique noble gas fractionation pattern for gas hydrates, one that shows promise in evaluating modern natural gas seeps for a signature associated with gas hydrate dissociation.

  1. Detection and Production of Methane Hydrate

    Energy Technology Data Exchange (ETDEWEB)

    George Hirasaki; Walter Chapman; Gerald Dickens; Colin Zelt; Brandon Dugan; Kishore Mohanty; Priyank Jaiswal

    2011-12-31

    This project seeks to understand regional differences in gas hydrate systems from the perspective of as an energy resource, geohazard, and long-term climate influence. Specifically, the effort will: (1) collect data and conceptual models that targets causes of gas hydrate variance, (2) construct numerical models that explain and predict regional-scale gas hydrate differences in 2-dimensions with minimal 'free parameters', (3) simulate hydrocarbon production from various gas hydrate systems to establish promising resource characteristics, (4) perturb different gas hydrate systems to assess potential impacts of hot fluids on seafloor stability and well stability, and (5) develop geophysical approaches that enable remote quantification of gas hydrate heterogeneities so that they can be characterized with minimal costly drilling. Our integrated program takes advantage of the fact that we have a close working team comprised of experts in distinct disciplines. The expected outcomes of this project are improved exploration and production technology for production of natural gas from methane hydrates and improved safety through understanding of seafloor and well bore stability in the presence of hydrates. The scope of this project was to more fully characterize, understand, and appreciate fundamental differences in the amount and distribution of gas hydrate and how this would affect the production potential of a hydrate accumulation in the marine environment. The effort combines existing information from locations in the ocean that are dominated by low permeability sediments with small amounts of high permeability sediments, one permafrost location where extensive hydrates exist in reservoir quality rocks and other locations deemed by mutual agreement of DOE and Rice to be appropriate. The initial ocean locations were Blake Ridge, Hydrate Ridge, Peru Margin and GOM. The permafrost location was Mallik. Although the ultimate goal of the project was to understand

  2. Gas Hydrates Research Programs: An International Review

    Energy Technology Data Exchange (ETDEWEB)

    Jorge Gabitto; Maria Barrufet

    2009-12-09

    Gas hydrates sediments have the potential of providing a huge amount of natural gas for human use. Hydrate sediments have been found in many different regions where the required temperature and pressure conditions have been satisfied. Resource exploitation is related to the safe dissociation of the gas hydrate sediments. Basic depressurization techniques and thermal stimulation processes have been tried in pilot efforts to exploit the resource. There is a growing interest in gas hydrates all over the world due to the inevitable decline of oil and gas reserves. Many different countries are interested in this valuable resource. Unsurprisingly, developed countries with limited energy resources have taken the lead in worldwide gas hydrates research and exploration. The goal of this research project is to collect information in order to record and evaluate the relative strengths and goals of the different gas hydrates programs throughout the world. A thorough literature search about gas hydrates research activities has been conducted. The main participants in the research effort have been identified and summaries of their past and present activities reported. An evaluation section discussing present and future research activities has also been included.

  3. Prospecting for marine gas hydrate resources

    Science.gov (United States)

    Boswell, Ray; Shipp, Craig; Reichel, Thomas; Shelander, Dianna; Saeki, Tetsuo; Frye, Matthew; Shedd, William; Collett, Timothy S.; McConnell, Daniel R.

    2016-01-01

    As gas hydrate energy assessment matures worldwide, emphasis has evolved away from confirmation of the mere presence of gas hydrate to the more complex issue of prospecting for those specific accumulations that are viable resource targets. Gas hydrate exploration now integrates the unique pressure and temperature preconditions for gas hydrate occurrence with those concepts and practices that are the basis for conventional oil and gas exploration. We have aimed to assimilate the lessons learned to date in global gas hydrate exploration to outline a generalized prospecting approach as follows: (1) use existing well and geophysical data to delineate the gas hydrate stability zone (GHSZ), (2) identify and evaluate potential direct indications of hydrate occurrence through evaluation of interval of elevated acoustic velocity and/or seismic events of prospective amplitude and polarity, (3) mitigate geologic risk via regional seismic and stratigraphic facies analysis as well as seismic mapping of amplitude distribution along prospective horizons, and (4) mitigate further prospect risk through assessment of the evidence of gas presence and migration into the GHSZ. Although a wide range of occurrence types might ultimately become viable energy supply options, this approach, which has been tested in only a small number of locations worldwide, has directed prospect evaluation toward those sand-hosted, high-saturation occurrences that were presently considered to have the greatest future commercial potential.

  4. Methane hydrate stability and anthropogenic climate change

    Directory of Open Access Journals (Sweden)

    D. Archer

    2007-04-01

    Full Text Available Methane frozen into hydrate makes up a large reservoir of potentially volatile carbon below the sea floor and associated with permafrost soils. This reservoir intuitively seems precarious, because hydrate ice floats in water, and melts at Earth surface conditions. The hydrate reservoir is so large that if 10% of the methane were released to the atmosphere within a few years, it would have an impact on the Earth's radiation budget equivalent to a factor of 10 increase in atmospheric CO2.

    Hydrates are releasing methane to the atmosphere today in response to anthropogenic warming, for example along the Arctic coastline of Siberia. However most of the hydrates are located at depths in soils and ocean sediments where anthropogenic warming and any possible methane release will take place over time scales of millennia. Individual catastrophic releases like landslides and pockmark explosions are too small to reach a sizable fraction of the hydrates. The carbon isotopic excursion at the end of the Paleocene has been interpreted as the release of thousands of Gton C, possibly from hydrates, but the time scale of the release appears to have been thousands of years, chronic rather than catastrophic.

    The potential climate impact in the coming century from hydrate methane release is speculative but could be comparable to climate feedbacks from the terrestrial biosphere and from peat, significant but not catastrophic. On geologic timescales, it is conceivable that hydrates could release much carbon to the atmosphere/ocean system as we do by fossil fuel combustion.

  5. METHANE HYDRATE PRODUCTION FROM ALASKAN PERMAFROST

    Energy Technology Data Exchange (ETDEWEB)

    Thomas E. Williams; Keith Millheim; Buddy King

    2004-03-01

    Natural-gas hydrates have been encountered beneath the permafrost and considered a nuisance by the oil and gas industry for years. Engineers working in Russia, Canada and the USA have documented numerous drilling problems, including kicks and uncontrolled gas releases, in arctic regions. Information has been generated in laboratory studies pertaining to the extent, volume, chemistry and phase behavior of gas hydrates. Scientists studying hydrate potential agree that the potential is great--on the North Slope of Alaska alone, it has been estimated at 590 TCF. However, little information has been obtained on physical samples taken from actual rock containing hydrates. This gas-hydrate project is in the second year of a three-year endeavor being sponsored by Maurer Technology, Noble, and Anadarko Petroleum, in partnership with the DOE. The purpose of the project is to build on previous and ongoing R&D in the area of onshore hydrate deposition. We plan to identify, quantify and predict production potential for hydrates located on the North Slope of Alaska. We also plan to design and implement a program to safely and economically drill, core and produce gas from arctic hydrates. The current work scope is to drill and core a well on Anadarko leases in FY 2003 and 2004. We are also using an on-site core analysis laboratory to determine some of the physical characteristics of the hydrates and surrounding rock. The well is being drilled from a new Anadarko Arctic Platform that will have minimal footprint and environmental impact. We hope to correlate geology, geophysics, logs, and drilling and production data to allow reservoir models to be calibrated. Ultimately, our goal is to form an objective technical and economic evaluation of reservoir potential in Alaska.

  6. Methane hydrate stability and anthropogenic climate change

    Directory of Open Access Journals (Sweden)

    D. Archer

    2007-07-01

    Full Text Available Methane frozen into hydrate makes up a large reservoir of potentially volatile carbon below the sea floor and associated with permafrost soils. This reservoir intuitively seems precarious, because hydrate ice floats in water, and melts at Earth surface conditions. The hydrate reservoir is so large that if 10% of the methane were released to the atmosphere within a few years, it would have an impact on the Earth's radiation budget equivalent to a factor of 10 increase in atmospheric CO2.

    Hydrates are releasing methane to the atmosphere today in response to anthropogenic warming, for example along the Arctic coastline of Siberia. However most of the hydrates are located at depths in soils and ocean sediments where anthropogenic warming and any possible methane release will take place over time scales of millennia. Individual catastrophic releases like landslides and pockmark explosions are too small to reach a sizable fraction of the hydrates. The carbon isotopic excursion at the end of the Paleocene has been interpreted as the release of thousands of Gton C, possibly from hydrates, but the time scale of the release appears to have been thousands of years, chronic rather than catastrophic.

    The potential climate impact in the coming century from hydrate methane release is speculative but could be comparable to climate feedbacks from the terrestrial biosphere and from peat, significant but not catastrophic. On geologic timescales, it is conceivable that hydrates could release as much carbon to the atmosphere/ocean system as we do by fossil fuel combustion.

  7. Dynamics of hydration water in protein

    International Nuclear Information System (INIS)

    Incoherent quasi-elastic neutron scattering studies of in vivo deuterated C-phycocyanin, at different levels of hydration, have been made. We show that the mobility at high temperature, (∝300 K) of the water molecules near the protein surface can be described by relatively simple models. At full hydration the high temperature data can be interpreted using a model where each water molecule is diffusing in a confined space of 3 A in radius. At low hydration, and 298 K, the diffusional behaviour is typical of jump diffusion with a residence time 10 times larger than the one in bulk water at the same temperature. (orig.)

  8. Tapping methane hydrates for unconventional natural gas

    Science.gov (United States)

    Ruppel, Carolyn

    2007-01-01

    Methane hydrate is an icelike form of concentrated methane and water found in the sediments of permafrost regions and marine continental margins at depths far shallower than conventional oil and gas. Despite their relative accessibility and widespread occurrence, methane hydrates have never been tapped to meet increasing global energy demands. With rising natural gas prices, production from these unconventional gas deposits is becoming economically viable, particularly in permafrost areas already being exploited for conventional oil and gas. This article provides an overview of gas hydrate occurrence, resource assessment, exploration, production technologies, renewability, and future challenges.

  9. Glass powder blended cement hydration modelling

    Science.gov (United States)

    Saeed, Huda

    The use of waste materials in construction is among the most attractive options to consume these materials without affecting the environment. Glass is among these types of potential waste materials. In this research, waste glass in powder form, i.e. glass powder (GP) is examined for potential use in enhancing the characteristics of concrete on the basis that it is a pozzolanic material. The experimental and the theoretical components of the work are carried out primarily to prove that glass powder belongs to the "family" of the pozzolanic materials. The chemical and physical properties of the hydrated activated glass powder and the hydrated glass powder cement on the microstructure level have been studied experimentally and theoretically. The work presented in this thesis consists of two main phases. The first phase contains experimental investigations of the reaction of glass powder with calcium hydroxide (CH) and water. In addition, it includes experiments that are aimed at determining the consumption of water and CH with time. The reactivity, degree of hydration, and nature of the pore solution of the glass powder-blended cement pastes and the effect of adding different ratios of glass powder on cement hydration is also investigated. The experiments proved that glass powder has a pozzolanic effect on cement hydration; hence it enhances the chemical and physical properties of cement paste. Based on the experimental test results, it is recommended to use a glass powder-to-cement ratio (GP/C) of 10% as an optimum ratio to achieve the best hydration and best properties of the paste. Two different chemical formulas for the produced GP C-S-H gel due to the pure GP and GP-CH pozzolanic reaction hydration are proposed. For the pure GP hydration, the produced GP C-S-H gel has a calcium-to-silica ratio (C/S) of 0.164, water-to-silica ratio (H/S) of 1.3 and sodium/silica ratio (N/S) of 0.18. However, for the GP-CH hydration, the produced GP C-S-H gel has a C/S ratio of 1

  10. Effect of Some Admixtures on the Hydration of Silica Fume and Hydrated Lime

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The effects of sodium salt of naphthalene formaldehyde sulfonic acid and stearic acid on the hydration of silica fume and Ca(0H)2 have been investigated. The hydration was carried out at 60℃ and W/S ratio of 4 for various time intervals namely, 1, 3, 7 and 28 days and in the presence of 0.2% and 5% superplasticizer and stearic acid. The results of the hydration kinetics show that both admixtures accelerate the hydration reaction of silica fume and calcium hydroxide during the first 7 days. Whereas, after 28 days hydration there is no significant effect. Generally, most of free calcium hydroxide seems to be consumed after 28 days. In addition, the phase composition as well as the microstructure of the formed hydrates was examined by using X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM) respectively.

  11. Experimental Investigation of Effect on Hydrate Formation in Spray Reactor

    Directory of Open Access Journals (Sweden)

    Jianzhong Zhao

    2015-01-01

    Full Text Available The effects of reaction condition on hydrate formation were conducted in spray reactor. The temperature, pressure, and gas volume of reaction on hydrate formation were measured in pure water and SDS solutions at different temperature and pressure with a high-pressure experimental rig for hydrate formation. The experimental data and result reveal that additives could improve the hydrate formation rate and gas storage capacity. Temperature and pressure can restrict the hydrate formation. Lower temperature and higher pressure can promote hydrate formation, but they can increase production cost. So these factors should be considered synthetically. The investigation will promote the advance of gas storage technology in hydrates.

  12. Pockmark formation and evolution in deep water Nigeria: Rapid hydrate growth versus slow hydrate dissolution

    OpenAIRE

    Sultan, Nabil; Bohrmann, G.; Ruffine, Livio; Pape, T.; Riboulot, Vincent; Colliat, J. -l.; De Prunele, Alexis; Dennielou, Bernard; Garziglia, Sebastien; Himmler, Tobias; Marsset, Tania; Peters, C. A.; Rabiu, A.; J. Wei

    2014-01-01

    In previous works, it has been suggested that dissolution of gas hydrate can be responsible for pockmark formation and evolution in deep water Nigeria. It was shown that those pockmarks which are at different stages of maturation are characterized by a common internal architecture associated to gas hydrate dynamics. New results obtained by drilling into gas hydrate-bearing sediments with the MeBo seafloor drill rig in concert with geotechnical in situ measurements and pore water analyses indi...

  13. ConocoPhillips Gas Hydrate Production Test

    Energy Technology Data Exchange (ETDEWEB)

    Schoderbek, David; Farrell, Helen; Howard, James; Raterman, Kevin; Silpngarmlert, Suntichai; Martin, Kenneth; Smith, Bruce; Klein, Perry

    2013-06-30

    Work began on the ConocoPhillips Gas Hydrates Production Test (DOE award number DE-NT0006553) on October 1, 2008. This final report summarizes the entire project from January 1, 2011 to June 30, 2013.

  14. Neutron cross section of methane hydrate

    Energy Technology Data Exchange (ETDEWEB)

    Kiyanagi, Y.; Date, S.; Horikawa, T.; Takamine, J.; Iwasa, H.; Kamiyama, T. [Graduate School of Eng., Hokkaido Univ., Sapporo (Japan); Uchida, T.; Ebinuma, T.; Narrita, H. [National Inst. of Advanced Industrial Science, Tsukisamu, Sapporo (Japan); Bennington, S.M. [ISIS Dept., Rutherford Appleton, Chilton, Didcot, Oxon (United Kingdom)

    2004-03-01

    To estimate the neutronic characteristics of methane hydrate and also to synthesize cross section data for simulation we need neutron scattering data ranging wide energy and momentum region. We performed inelastic neutron scattering experiments to get information about the neutron cross section on methane hydrate. It was found that at high momentum transfer region rotational mode as well as vibration mode showed recoil like behavior. On the other hand, at low momentum region, as well known, free rotation like energy levels were observed. The energy level of ice in methane hydrate was very similar to normal ice. The results suggest that the rough expression of the cross section of the methane hydrate is presented by linear combination of the methane and ice. (orig.)

  15. Hydrate Control for Gas Storage Operations

    Energy Technology Data Exchange (ETDEWEB)

    Jeffrey Savidge

    2008-10-31

    The overall objective of this project was to identify low cost hydrate control options to help mitigate and solve hydrate problems that occur in moderate and high pressure natural gas storage field operations. The study includes data on a number of flow configurations, fluids and control options that are common in natural gas storage field flow lines. The final phase of this work brings together data and experience from the hydrate flow test facility and multiple field and operator sources. It includes a compilation of basic information on operating conditions as well as candidate field separation options. Lastly the work is integrated with the work with the initial work to provide a comprehensive view of gas storage field hydrate control for field operations and storage field personnel.

  16. Polyethylene oxide hydration in grafted layers

    Science.gov (United States)

    Dormidontova, Elena; Wang, Zilu

    Hydration of water soluble polymers is one of the key-factors defining their conformation and properties, similar to biopolymers. Polyethylene oxide (PEO) is one of the most important biomedical-applications polymers and is known for its reverse temperature solubility due to hydrogen bonding with water. As in many practical applications PEO chains are grafted to surfaces, e.g. of nanoparticles or planar surfaces, it is important to understand PEO hydration in such grafted layers. Using atomistic molecular dynamic simulations we investigate the details of molecular conformation and hydration of PEO end-grafted to gold surfaces. We analyze polymer and water density distribution as a function of distance from the surface for different grafting densities. Based on a detailed analysis of hydrogen bonding between polymer and water in grafted PEO layers, we will discuss the extent of PEO hydration and its implication for polymer conformation, mobility and layer properties. This research is supported by NSF (DMR-1410928).

  17. Vibrational dynamics of hydration water in amylose

    CERN Document Server

    Cavatorta, F; Albanese, G; Angelini, N

    2002-01-01

    We present a study of the dynamical properties of hydration water associated with amylose helices, based on low-temperature vibrational spectra collected using the TOSCA inelastic spectrometer at ISIS. The structural constraints of the polysaccharidic chains favour the formation of a high-density structure for water, which has been suggested by Imberty and Perez on the basis of conformational analysis. According to this model, hydration water can only enter the pores formed by six adjacent helices and completely fills the pores at a hydration level of about 0.27-g water/g dry amylose. Our measurements show that the dynamical behaviour of hydration water is similar to that observed in high-density amorphous ice. (orig.)

  18. Coupled multiphysics modeling of gas hydrate bearing sediments

    OpenAIRE

    Sanchez, Marcelo; Gai, Xuerui; Santamarina, J. Carlos

    2014-01-01

    Gas hydrates are crystalline clathrate compounds made of water and a low molecular gas like methane (Sloan 1998). Gas hydrates are generally present in oil-producing areas and in permafrost regions. Methane hydrate deposits can lead to large-scale submarine slope failures, blowouts, platform foundation failures, and -borehole instability. Gas hydrates constitute also an attractive source of energy as they are estimated to contain very large reserves of methane. Hydrate formation, dissociation...

  19. Experimental Investigation of Effect on Hydrate Formation in Spray Reactor

    OpenAIRE

    Jianzhong Zhao; Yaqin Tian; Yangsheng Zhao; Wenping Cheng

    2015-01-01

    The effects of reaction condition on hydrate formation were conducted in spray reactor. The temperature, pressure, and gas volume of reaction on hydrate formation were measured in pure water and SDS solutions at different temperature and pressure with a high-pressure experimental rig for hydrate formation. The experimental data and result reveal that additives could improve the hydrate formation rate and gas storage capacity. Temperature and pressure can restrict the hydrate formation. Lower ...

  20. METHANE HYDRATE PRODUCTION FROM ALASKAN PERMAFROST

    Energy Technology Data Exchange (ETDEWEB)

    Ali Kadaster; Bill Liddell; Tommy Thompson; Thomas Williams; Michael Niedermayr

    2005-02-01

    Natural-gas hydrates have been encountered beneath the permafrost and considered a nuisance by the oil and gas industry for years. Engineers working in Russia, Canada and the USA have documented numerous drilling problems, including kicks and uncontrolled gas releases, in arctic regions. Information has been generated in laboratory studies pertaining to the extent, volume, chemistry and phase behavior of gas hydrates. Scientists studying hydrate potential agree that the potential is great--on the North Slope of Alaska alone, it has been estimated at 590 TCF. However, little information has been obtained on physical samples taken from actual rock containing hydrates. This gas-hydrate project was a cost-shared partnership between Maurer Technology, Noble Corporation, Anadarko Petroleum, and the U.S. Department of Energy's Methane Hydrate R&D program. The purpose of the project is to build on previous and ongoing R&D in the area of onshore hydrate deposition to identify, quantify and predict production potential for hydrates located on the North Slope of Alaska. The work scope included drilling and coring a well (Hot Ice No. 1) on Anadarko leases beginning in FY 2003 and completed in 2004. During the first drilling season, operations were conducted at the site between January 28, 2003 to April 30, 2003. The well was spudded and drilled to a depth of 1403 ft. Due to the onset of warmer weather, work was then suspended for the season. Operations at the site were continued after the tundra was re-opened the following season. Between January 12, 2004 and March 19, 2004, the well was drilled and cored to a final depth of 2300 ft. An on-site core analysis laboratory was built and implemented for determining physical characteristics of the hydrates and surrounding rock. The well was drilled from a new Anadarko Arctic Platform that has a minimal footprint and environmental impact. Final efforts of the project are to correlate geology, geophysics, logs, and drilling and

  1. METHANE HYDRATE PRODUCTION FROM ALASKAN PERMAFROST

    Energy Technology Data Exchange (ETDEWEB)

    Thomas E. Williams; Keith Millheim; Bill Liddell

    2004-11-01

    Natural-gas hydrates have been encountered beneath the permafrost and considered a nuisance by the oil and gas industry for years. Engineers working in Russia, Canada and the USA have documented numerous drilling problems, including kicks and uncontrolled gas releases, in arctic regions. Information has been generated in laboratory studies pertaining to the extent, volume, chemistry and phase behavior of gas hydrates. Scientists studying hydrate potential agree that the potential is great--on the North Slope of Alaska alone, it has been estimated at 590 TCF. However, little information has been obtained on physical samples taken from actual rock containing hydrates. This gas-hydrate project is a cost-shared partnership between Maurer Technology, Anadarko Petroleum, Noble Corporation, and the U.S. Department of Energy's Methane Hydrate R&D program. The purpose of the project is to build on previous and ongoing R&D in the area of onshore hydrate deposition to help identify, quantify and predict production potential for hydrates located on the North Slope of Alaska. As part of the project work scope, team members drilled and cored a well (the Hot Ice No. 1) on Anadarko leases beginning in January 2003 and completed in March 2004. Due to scheduling constraints imposed by the Arctic drilling season, operations at the site were suspended between April 21, 2003 and January 30, 2004. An on-site core analysis laboratory was constructed and used for determining physical characteristics of frozen core immediately after it was retrieved from the well. The well was drilled from a new and innovative Anadarko Arctic Platform that has a greatly reduced footprint and environmental impact. Final efforts of the project were to correlate geology, geophysics, logs, and drilling and production data and provide this information to scientists for future hydrate operations. No gas hydrates were encountered in this well; however, a wealth of information was generated and is contained

  2. METHANE HYDRATE PRODUCTION FROM ALASKAN PERMAFROST

    Energy Technology Data Exchange (ETDEWEB)

    Thomas E. Williams; Keith Millheim; Bill Liddell

    2005-02-01

    Natural-gas hydrates have been encountered beneath the permafrost and considered a nuisance by the oil and gas industry for years. Engineers working in Russia, Canada and the USA have documented numerous drilling problems, including kicks and uncontrolled gas releases, in arctic regions. Information has been generated in laboratory studies pertaining to the extent, volume, chemistry and phase behavior of gas hydrates. Scientists studying hydrate potential agree that the potential is great--on the North Slope of Alaska alone, it has been estimated at 590 TCF. However, little information has been obtained on physical samples taken from actual rock containing hydrates. This gas-hydrate project is a cost-shared partnership between Maurer Technology, Anadarko Petroleum, Noble Corporation, and the U.S. Department of Energy's Methane Hydrate R&D program. The purpose of the project is to build on previous and ongoing R&D in the area of onshore hydrate deposition to help identify, quantify and predict production potential for hydrates located on the North Slope of Alaska. As part of the project work scope, team members drilled and cored a well (the Hot Ice No. 1) on Anadarko leases beginning in January 2003 and completed in March 2004. Due to scheduling constraints imposed by the Arctic drilling season, operations at the site were suspended between April 21, 2003 and January 30, 2004. An on-site core analysis laboratory was constructed and used for determining physical characteristics of frozen core immediately after it was retrieved from the well. The well was drilled from a new and innovative Anadarko Arctic Platform that has a greatly reduced footprint and environmental impact. Final efforts of the project were to correlate geology, geophysics, logs, and drilling and production data and provide this information to scientists for future hydrate operations. No gas hydrates were encountered in this well; however, a wealth of information was generated and is contained

  3. METHANE HYDRATE PRODUCTION FROM ALASKAN PERMAFROST

    Energy Technology Data Exchange (ETDEWEB)

    Steve Runyon; Mike Globe; Kent Newsham; Robert Kleinberg; Doug Griffin

    2005-02-01

    Natural-gas hydrates have been encountered beneath the permafrost and considered a nuisance by the oil and gas industry for years. Engineers working in Russia, Canada and the USA have documented numerous drilling problems, including kicks and uncontrolled gas releases, in arctic regions. Information has been generated in laboratory studies pertaining to the extent, volume, chemistry and phase behavior of gas hydrates. Scientists studying hydrate potential agree that the potential is great--on the North Slope of Alaska alone, it has been estimated at 590 TCF. However, little information has been obtained on physical samples taken from actual rock containing hydrates. This gas-hydrate project was a cost-shared partnership between Maurer Technology, Noble Corporation, Anadarko Petroleum, and the U.S. Department of Energy's Methane Hydrate R&D program. The purpose of the project is to build on previous and ongoing R&D in the area of onshore hydrate deposition to identify, quantify and predict production potential for hydrates located on the North Slope of Alaska. The work scope included drilling and coring a well (Hot Ice No. 1) on Anadarko leases beginning in FY 2003 and completed in 2004. During the first drilling season, operations were conducted at the site between January 28, 2003 to April 30, 2003. The well was spudded and drilled to a depth of 1403 ft. Due to the onset of warmer weather, work was then suspended for the season. Operations at the site were continued after the tundra was re-opened the following season. Between January 12, 2004 and March 19, 2004, the well was drilled and cored to a final depth of 2300 ft. An on-site core analysis laboratory was built and utilized for determining the physical characteristics of the hydrates and surrounding rock. The well was drilled from a new Anadarko Arctic Platform that has a minimal footprint and environmental impact. The final efforts of the project are to correlate geology, geophysics, logs, and drilling

  4. Experimental Dissociation of Methane Hydrates Through Depressurization

    Science.gov (United States)

    Borgfeldt, T.; Flemings, P. B.; Meyer, D.; You, K.

    2015-12-01

    We dissociated methane hydrates by stepwise depressurization. The initial hydrates were formed by injecting gas into a cylindrical sample of brine-saturated, coarse-grained sand at hydrate-stable conditions with the intention of reaching three-phase equilibrium. The sample was initially at 1°C with a pore pressure of 1775 psi and a salinity of 7 wt. % NaBr. The depressurization setup consisted of one pump filled with tap water attached to the confining fluid port and a second pump attached to the inlet port where the methane was injected. Depressurization was conducted over sixteen hours at a constant temperature of 1°C. The pore pressure was stepwise reduced from 1775 psi to atmospheric pressure by pulling known volumes of gas from the sample. After each extraction, we recorded the instantaneous and equilibrium pore pressure. 0.503 moles of methane were removed from the sample. The pore pressure decreased smoothly and nonlinearly with the cumulative gas withdrawn from the sample. We interpret that hydrate began to dissociate immediately with depressurization, and it continued to dissociate when the pressure decreased below the three-phase pressure for 1°C and 0 wt. % salinity. Two breaks in slope in the pressure vs. mass extracted data are bounded by smooth, nonlinear curves with differing slopes on either side. We attribute the breaks to dissociation of three zones of hydrate concentration. We created a box model to simulate the experimental behavior. For a 10% initial gas saturation (estimated from the hydrate formation experiment and based on mass conservation), an initial hydrate saturation of 55% is required to match the total methane extracted from the sample. Future experiments will be conducted over a longer timespan while monitoring hydrate dissociation with CT imaging throughout the process.

  5. Intermolecular Hydrogen Transfer in Isobutane Hydrate

    OpenAIRE

    Takeshi Sugahara; Kei Takeya; Mikio Nakagoshi; Takashi Minami; Atsushi Tani; Naohiro Kobayashi; Kazunari Ohgaki

    2012-01-01

    Electron spin resonance (ESR) spectra of butyl radicals induced with γ-ray irradiation in the simple isobutane (2-methylpropane) hydrate (prepared with deuterated water) were investigated. Isothermal annealing results of the γ-ray-irradiated isobutane hydrate reveal that the isobutyl radical in a large cage withdraws a hydrogen atom from the isobutane molecule through shared hexagonal-faces of adjacent large cages. During this “hydrogen picking” process, the isobutyl radical is apparently tra...

  6. Exploitation of subsea gas hydrate reservoirs

    Science.gov (United States)

    Janicki, Georg; Schlüter, Stefan; Hennig, Torsten; Deerberg, Görge

    2016-04-01

    Natural gas hydrates are considered to be a potential energy resource in the future. They occur in permafrost areas as well as in subsea sediments and are stable at high pressure and low temperature conditions. According to estimations the amount of carbon bonded in natural gas hydrates worldwide is two times larger than in all known conventional fossil fuels. Besides technical challenges that have to be overcome climate and safety issues have to be considered before a commercial exploitation of such unconventional reservoirs. The potential of producing natural gas from subsea gas hydrate deposits by various means (e.g. depressurization and/or injection of carbon dioxide) is numerically studied in the frame of the German research project »SUGAR«. The basic mechanisms of gas hydrate formation/dissociation and heat and mass transport in porous media are considered and implemented into a numerical model. The physics of the process leads to strong non-linear couplings between hydraulic fluid flow, hydrate dissociation and formation, hydraulic properties of the sediment, partial pressures and seawater solution of components and the thermal budget of the system described by the heat equation. This paper is intended to provide an overview of the recent development regarding the production of natural gas from subsea gas hydrate reservoirs. It aims at giving a broad insight into natural gas hydrates and covering relevant aspects of the exploitation process. It is focused on the thermodynamic principles and technological approaches for the exploitation. The effects occurring during natural gas production within hydrate filled sediment layers are identified and discussed by means of numerical simulation results. The behaviour of relevant process parameters such as pressure, temperature and phase saturations is described and compared for different strategies. The simulations are complemented by calculations for different safety relevant problems.

  7. Hydration during intense exercise training.

    Science.gov (United States)

    Maughan, R J; Meyer, N L

    2013-01-01

    Hydration status has profound effects on both physical and mental performance, and sports performance is thus critically affected. Both overhydration and underhydration - if sufficiently severe - will impair performance and pose a risk to health. Athletes may begin exercise in a hypohydrated state as a result of incomplete recovery from water loss induced in order to achieve a specific body mass target or due to incomplete recovery from a previous competition or training session. Dehydration will also develop in endurance exercise where fluid intake does not match water loss. The focus has generally been on training rather than on competition, but sweat loss and fluid replacement in training may have important implications. Hypohydration may impair training quality and may also increase stress levels. It is unclear whether this will have negative effects (reduced training quality, impaired immunity) or whether it will promote a greater adaptive response. Hypohydration and the consequent hyperthermia, however, can enhance the effectiveness of a heat acclimation program, resulting in improved endurance performance in warm and temperate environments. Drinking in training may be important in enhancing tolerance of the gut when athletes plan to drink in competition. The distribution of water between body water compartments may also be important in the initiation and promotion of cellular adaptations to the training stimulus. PMID:23899752

  8. Phase Transition of Methane Gas Hydrate and Response of Marine Gas Hydrate Systems to Environmental Changes

    Science.gov (United States)

    Xu, W.

    2003-12-01

    Gas hydrates, which contain mostly methane as the gas component in marine sediment, are stable under relatively high pressure and low temperature conditions such as those found along continental margins and permafrost regions. Its stability is mostly controlled by in-situ pressure, temperature and salinity of pore fluid. Environmentally introduced changes in pressure and temperature can affect the stability of gas hydrate in marine sediment. While certain changes may enhance the process of gas hydrate formation, we are much more interested in the resultant dissociation processes, which may contribute to sub-marine slope instability, seafloor sediment failure, formation of mud volcanoes and pock marks, potential vulnerability of engineering structures, and the risk to drilling and production. We have been developing models to quantify phase transition processes of marine gas hydrates and to investigate the response of marine gas hydrate systems to environmental changes. Methane gas hydrate system is considered as a three-component (water, methane, salt) four-phase (liquid, gas, hydrate, halite) system. Pressure, temperature and salinity of pore fluid constrain the stability of gas hydrate and affect phase transition processes via their effects on methane solubility and fluid density and enthalpy. Compared to the great quantity of studies on its stability in the literature, in-depth research on phase transition of gas hydrate is surprisingly much less. A method, which employs pressure, enthalpy, salinity and methane content as independent variables, is developed to calculate phase transition processes of the three-component four-phase system. Temperature, an intensive thermodynamic parameter, is found not sufficient in describing phase transition of gas hydrate. The extensive thermodynamic parameter enthalpy, on the other hand, is found to be sufficient both in calculation of the phase transition processes and in modeling marine gas hydrate systems. Processes

  9. Hydrate pingoes at Nyegga: some characteristic features

    Science.gov (United States)

    Hovland, M.

    2009-04-01

    Hydrate pingoes were observed on the seafloor during two different remotely operated vehicle (ROV)-dives, conducted by Statoil at complex-pockmark G11, at Nyegga, off Mid-Norway. Confirmation that these structures actually represent hydrate ice-cored sediment mounds (pingoes), was done by other investigators (Ivanov et al., 2006). Because it is expected that hydrate pingoes represent relatively dynamic seafloor topographic structures and that their shape and size most probably will change over relatively short time, it is important to know how to recognise them visually. Hovland and Svensen (2006) highlighted five different characteristic aspects that define hydrate pingoes on the sea floor: 1) They are dome- or disc-shaped features, which may attain any size from ~0.5 m in height and upwards. Inside pockmark G11, they were up to 1 m high. 2) They are circular or oval in plan view and may attain lateral sizes on the seafloor ranging upwards from ~0.5 m. Inside G11 they had lengths of several metres and widths of up to 4 m. 3) They have dense communities of organisms growing on their surfaces. At G11, they were overgrown with small pogonophoran tube-worms. 4) They have patches of white or grey bacterial mats growing on their surface, indicating advection (seepage) of reduced pore-waters. 5) They have small pits and patches of fluidized sediments on their surface, indicating pit corrosion of the sub-surface gas hydrate. Because gas hydrates often form in high-porosity, near-surface sediments, where water is readily available, it is thought that they will build up at locations where gases are actively migrating upwards from depth. However, gas hydrates are not stable in the presence of ambient seawater, as seawater is deficient in guest molecule gases (normally methane). Therefore, they tend to build up below surface above conduits for gas flow from depth. But, the near-surface hydrate ice-lenses will continually be corroded by seawater circulating into the sediments

  10. Distinguishing between hydrated, partially hydrated or unhydrated clinker in hardened concrete using microscopy

    NARCIS (Netherlands)

    Valcke, S.L.A.; Rooij, M.R. de; Visser, J.H.M.; Nijland, T.G.

    2010-01-01

    Hydration of clinker particles is since long a topic of interest in both designing and optimizing cement composition and its quantity used in concrete. The interest for carefully observing and also quantifying the type or stage of clinker hydration in hardened cement paste is twofold. Firstly, the c

  11. Hydrate-phobic surfaces: fundamental studies in clathrate hydrate adhesion reduction.

    Science.gov (United States)

    Smith, J David; Meuler, Adam J; Bralower, Harrison L; Venkatesan, Rama; Subramanian, Sivakumar; Cohen, Robert E; McKinley, Gareth H; Varanasi, Kripa K

    2012-05-01

    Clathrate hydrate formation and subsequent plugging of deep-sea oil and gas pipelines represent a significant bottleneck for deep-sea oil and gas operations. Current methods for hydrate mitigation are expensive and energy intensive, comprising chemical, thermal, or flow management techniques. In this paper, we present an alternate approach of using functionalized coatings to reduce hydrate adhesion to surfaces, ideally to a low enough level that hydrodynamic shear stresses can detach deposits and prevent plug formation. Systematic and quantitative studies of hydrate adhesion on smooth substrates with varying solid surface energies reveal a linear trend between hydrate adhesion strength and the practical work of adhesion (γ(total)[1 + cos θ(rec)]) of a suitable probe liquid, that is, one with similar surface energy properties to those of the hydrate. A reduction in hydrate adhesion strength by more than a factor of four when compared to bare steel is achieved on surfaces characterized by low Lewis acid, Lewis base, and van der Waals contributions to surface free energy such that the practical work of adhesion is minimized. These fundamental studies provide a framework for the development of hydrate-phobic surfaces, and could lead to passive enhancement of flow assurance and prevention of blockages in deep-sea oil and gas operations. PMID:22441203

  12. Kinetic studies of gas hydrate formation with low-dosage hydrate inhibitors

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Pipeline blockage by gas hydrates is a serious problem in the petroleum industry.Low-dosage inhibitors have been developed for its cost-effective and environmentally acceptable characteristics.In a 1.072-L reactor with methane,ethane and propane gas mixture under the pressure of about 8.5 MPa at 4 °C,hydrate formation was investigated with low-dosage hydrate inhibitors PVP and GHI1,the change of the compressibility factor and gas composition in the gas phase was analyzed,the gas contents in hydrates were compared with PVP and GHI1 added,and the inhibition mechanism of GHI1 was discussed.The results show that PVP and GHI1 could effectively inhibit the growth of gas hydrates but not nucleation.Under the experimental condition with PVP added,methane and ethane occupied the small cavities of the hydrate crystal unit and the ability of ethane entering into hydrate cavities was weaker than that of methane.GHI1 could effectively inhibit molecules which could more readily form hydrates.The ether and hydroxy group of diethylene glycol monobutyl ether have the responsibility for stronger inhibition ability of GHI1 than PVP.

  13. Controls on Gas Hydrate Formation and Dissociation

    Energy Technology Data Exchange (ETDEWEB)

    Miriam Kastner; Ian MacDonald

    2006-03-03

    The main objectives of the project were to monitor, characterize, and quantify in situ the rates of formation and dissociation of methane hydrates at and near the seafloor in the northern Gulf of Mexico, with a focus on the Bush Hill seafloor hydrate mound; to record the linkages between physical and chemical parameters of the deposits over the course of one year, by emphasizing the response of the hydrate mound to temperature and chemical perturbations; and to document the seafloor and water column environmental impacts of hydrate formation and dissociation. For these, monitoring the dynamics of gas hydrate formation and dissociation was required. The objectives were achieved by an integrated field and laboratory scientific study, particularly by monitoring in situ formation and dissociation of the outcropping gas hydrate mound and of the associated gas-rich sediments. In addition to monitoring with the MOSQUITOs, fluid flow rates and temperature, continuously sampling in situ pore fluids for the chemistry, and imaging the hydrate mound, pore fluids from cores, peepers and gas hydrate samples from the mound were as well sampled and analyzed for chemical and isotopic compositions. In order to determine the impact of gas hydrate dissociation and/or methane venting across the seafloor on the ocean and atmosphere, the overlying seawater was sampled and thoroughly analyzed chemically and for methane C isotope ratios. At Bush hill the pore fluid chemistry varies significantly over short distances as well as within some of the specific sites monitored for 440 days, and gas venting is primarily focused. The pore fluid chemistry in the tub-warm and mussel shell fields clearly documented active gas hydrate and authigenic carbonate formation during the monitoring period. The advecting fluid is depleted in sulfate, Ca Mg, and Sr and is rich in methane; at the main vent sites the fluid is methane supersaturated, thus bubble plumes form. The subsurface hydrology exhibits both

  14. Depressurization and electrical heating of hydrate sediment for gas production

    Science.gov (United States)

    Minagawa, H.

    2015-12-01

    As a part of a Japanese National hydrate research program (MH21, funded by METI), we performed a study on electrical heating of the hydrate core combined with depressurization for gas production. In-situ dissociation of natural gas hydrate is necessary for commercial recovery of natural gas from natural gas hydrate sediment. Thermal stimulation is an effective dissociation method, along with depressurization.To simulate methane gas production from methane hydrate layer, we investigated electrical heating of methane hydrate sediment. A decrease in core temperature due to the endothermic reaction of methane hydrate dissociation was suppressed and the core temperature increased between 1oC and 4oC above the control temperature with electric heating. A current density of 10A/m2 with depressurization would effectively dissociate hydrate. Therefore, depressurization and additional electrode heating of hydrate sediment saturated with electrolyte solution was confirmed to enable higher gas production from sediment with less electric power.

  15. Properties of equilibrium carbon dioxide hydrate in porous medium

    Science.gov (United States)

    Voronov, V. P.; Gorodetskii, E. E.; Podnek, V. E.; Grigoriev, B. A.

    2016-09-01

    Specific heat capacity, dissociation heat and hydration number of carbon dioxide hydrate in porous medium are determined by adiabatic calorimetry method. The measurements were carried out in the temperature range 250-290 K and in pressure range 1-5 MPa. The measured specific heat of the hydrate is approximately 2.7 J/(g K), which is significantly larger than the specific heat of methane hydrate. In particular, at heating, larger value of the specific heat of carbon dioxide hydrate is a result of gas emission from the hydrate. The hydration number at the hydrate-gas coexistence changes from 6.2 to 6.9. The dissociation heat of carbon dioxide hydrate varies from the 55 kJ/mol near the upper quadruple point to the 57 kJ/mol near the lower quadruple point.

  16. Thermodynamic modeling for clathrate hydrates of ozone

    International Nuclear Information System (INIS)

    Highlights: • We present a phase-equilibrium model for ozone-containing clathrate hydrates. • We determine intermolecular potential parameters for O3. • There is good agreement between the developed model and the experimental data. • The results show the capability of O3 as a guest substance for clathrate hydrates. • We perform parametric studies for O3 storage capacity with various thermodynamic conditions. -- Abstract: We report a theoretical study to predict the phase-equilibrium properties of ozone-containing clathrate hydrates based on the statistical thermodynamics model developed by van der Waals and Platteeuw. The Patel–Teja–Valderrama equation of state is employed for an accurate estimation of the properties of gas phase ozone. We determined the three parameters of the Kihara intermolecular potential for ozone as a = 6.815 · 10−2 nm, σ = 2.9909 · 10−1 nm, and ε · kB−1 = 184.00 K. An infinite set of ε–σ parameters for ozone were determined, reproducing the experimental phase equilibrium pressure–temperature data of the (O3 + O2 + CO2) clathrate hydrate. A unique parameter pair was chosen based on the experimental ozone storage capacity data for the (O3 + O2 + CCl4) hydrate that we reported previously. The prediction with the developed model showed good agreement with the experimental phase equilibrium data within ±2% of the average deviation of the pressure. The Kihara parameters of ozone showed slightly better suitability for the structure-I hydrate than CO2, which was used as a help guest. Our model suggests the possibility of increasing the ozone storage capacity of clathrate hydrates (∼7% on a mass basis) from the previously reported experimental capacity (∼1%)

  17. Experimental characterization of production behavior accompanying the hydrate reformation in methane hydrate bearing sediments

    Energy Technology Data Exchange (ETDEWEB)

    Ahn, T.; Kang, J.M.; Nguyen, H.T. [Seoul National Univ., Seoul (Korea, Republic of); Park, C. [Kangwon National Univ., (Korea, Republic of); Lee, J. [Korea Inst., of Geoscience and Mineral Resources (Korea, Republic of)

    2010-07-01

    This study investigated the production behaviour associated with gas hydrate reformation in methane hydrate-bearing sediment by hot-brine injection. A range of different temperature and brine injection rates were used to analyze the pressure and temperature distribution, the gas production behaviour and the movement of the dissociation front. The study showed that hydrate reformation reduces the production rate considerably at an early time. However, gas production increases during the dissociation, near the outlet because the dissociated methane around the inlet is consumed in reforming the hydrate and increases the hydrate saturation around the outlet. Higher temperature also increases the gas production rate and the speed of the dissociation front. 12 refs., 2 tabs., 4 figs.

  18. Authigenic gypsum found in gas hydrate-associated sediments from Hydrate Ridge, the eastern North Pacific

    Institute of Scientific and Technical Information of China (English)

    WANG Jiasheng; Erwin Suess; Dirk Rickert

    2004-01-01

    Characteristic gypsum micro-sphere and granular mass were discovered by binocular microscope in the gas hydrate-associated sediments at cores SO143-221 and SO143/TVG40-2A respectively on Hydrate Ridge of Cascadia margin, the eastern North Pacific. XRD patterns and EPA analyses show both micro-sphere and granular mass of the crystals have the typical peaks and the typical main chemical compositions of gypsum, although their weight percents are slightly less than the others in the non-gas hydrate-associated marine regions. SEM pictures show that the gypsum crystals have clear crystal boundaries, planes, edges and cleavages of gypsum in form either of single crystal or of twin crystals. In view of the fact that there are meanwhile gas hydrate-associated authigenic carbonates and SO42(-rich pore water in the same sediment cores, it could be inferred reasonably that the gypsums formed also authigenically in the gas hydrate-associated environment too, most probably at the interface between the downward advecting sulfate-rich seawater and the below gas hydrate, which spilled calcium during its formation on Hydrate Ridge. The two distinct forms of crystal intergrowth, which are the granular mass of series single gypsum crystals at core SO143/TVG40-2A and the microsphere of gypsum crystals accompanied with detrital components at core SO143-221 respectively, indicate that they precipitated most likely in different interstitial water dynamic environments. So, the distinct authigenic gypsums found in gas hydrate-associated sediments on Hydrate Ridge could also be believed as one of the parameters which could be used to indicate the presence of gas hydrate in an unknown marine sediment cores.

  19. METHANE HYDRATE PRODUCTION FROM ALASKAN PERMAFROST

    Energy Technology Data Exchange (ETDEWEB)

    Richard Sigal; Kent Newsham; Thomas Williams; Barry Freifeld; Timothy Kneafsey; Carl Sondergeld; Shandra Rai; Jonathan Kwan; Stephen Kirby; Robert Kleinberg; Doug Griffin

    2005-02-01

    Natural-gas hydrates have been encountered beneath the permafrost and considered a nuisance by the oil and gas industry for years. Engineers working in Russia, Canada and the USA have documented numerous drilling problems, including kicks and uncontrolled gas releases, in arctic regions. Information has been generated in laboratory studies pertaining to the extent, volume, chemistry and phase behavior of gas hydrates. Scientists studying hydrate potential agree that the potential is great--on the North Slope of Alaska alone, it has been estimated at 590 TCF. However, little information has been obtained on physical samples taken from actual rock containing hydrates. The work scope drilled and cored a well The Hot Ice No. 1 on Anadarko leases beginning in FY 2003 and completed in 2004. An on-site core analysis laboratory was built and utilized for determining the physical characteristics of the hydrates and surrounding rock. The well was drilled from a new Anadarko Arctic Platform that has a minimal footprint and environmental impact. The final efforts of the project are to correlate geology, geophysics, logs, and drilling and production data and provide this information to scientists developing reservoir models. No gas hydrates were encountered in this well; however, a wealth of information was generated and is contained in this report. The Hot Ice No. 1 well was drilled from the surface to a measured depth of 2300 ft. There was almost 100% core recovery from the bottom of surface casing at 107 ft to total depth. Based on the best estimate of the bottom of the methane hydrate stability zone (which used new data obtained from Hot Ice No. 1 and new analysis of data from adjacent wells), core was recovered over its complete range. Approximately 580 ft of porous, mostly frozen, sandstone and 155 of conglomerate were recovered in the Ugnu Formation and approximately 215 ft of porous sandstone were recovered in the West Sak Formation. There were gas shows in the bottom

  20. Development of hydrate risk quantification in oil and gas production

    Science.gov (United States)

    Chaudhari, Piyush N.

    Subsea flowlines that transport hydrocarbons from wellhead to the processing facility face issues from solid deposits such as hydrates, waxes, asphaltenes, etc. The solid deposits not only affect the production but also pose a safety concern; thus, flow assurance is significantly important in designing and operating subsea oil and gas production. In most subsea oil and gas operations, gas hydrates form at high pressure and low temperature conditions, causing the risk of plugging flowlines, with a undesirable impact on production. Over the years, the oil and gas industry has shifted their perspective from hydrate avoidance to hydrate management given several parameters such as production facility, production chemistry, economic and environmental concerns. Thus, understanding the level of hydrate risk associated with subsea flowlines is an important in developing efficient hydrate management techniques. In the past, hydrate formation models were developed for various flow-systems (e.g., oil dominated, water dominated, and gas dominated) present in the oil and gas production. The objective of this research is to extend the application of the present hydrate prediction models for assessing the hydrate risk associated with subsea flowlines that are prone to hydrate formation. It involves a novel approach for developing quantitative hydrate risk models based on the conceptual models built from the qualitative knowledge obtained from experimental studies. A comprehensive hydrate risk model, that ranks the hydrate risk associated with the subsea production system as a function of time, hydrates, and several other parameters, which account for inertial, viscous, interfacial forces acting on the flow-system, is developed for oil dominated and condensate systems. The hydrate plugging risk for water dominated systems is successfully modeled using The Colorado School of Mines Hydrate Flow Assurance Tool (CSMHyFAST). It is found that CSMHyFAST can be used as a screening tool in

  1. Complex admixtures of clathrate hydrates in a water desalination method

    Science.gov (United States)

    Simmons, Blake A.; Bradshaw, Robert W.; Dedrick, Daniel E.; Anderson, David W.

    2009-07-14

    Disclosed is a method that achieves water desalination by utilizing and optimizing clathrate hydrate phenomena. Clathrate hydrates are crystalline compounds of gas and water that desalinate water by excluding salt molecules during crystallization. Contacting a hydrate forming gaseous species with water will spontaneously form hydrates at specific temperatures and pressures through the extraction of water molecules from the bulk phase followed by crystallite nucleation. Subsequent dissociation of pure hydrates yields fresh water and, if operated correctly, allows the hydrate-forming gas to be efficiently recycled into the process stream.

  2. Gas hydrates: past and future geohazard?

    Science.gov (United States)

    Maslin, Mark; Owen, Matthew; Betts, Richard; Day, Simon; Dunkley Jones, Tom; Ridgwell, Andrew

    2010-05-28

    Gas hydrates are ice-like deposits containing a mixture of water and gas; the most common gas is methane. Gas hydrates are stable under high pressures and relatively low temperatures and are found underneath the oceans and in permafrost regions. Estimates range from 500 to 10,000 giga tonnes of carbon (best current estimate 1600-2000 GtC) stored in ocean sediments and 400 GtC in Arctic permafrost. Gas hydrates may pose a serious geohazard in the near future owing to the adverse effects of global warming on the stability of gas hydrate deposits both in ocean sediments and in permafrost. It is still unknown whether future ocean warming could lead to significant methane release, as thermal penetration of marine sediments to the clathrate-gas interface could be slow enough to allow a new equilibrium to occur without any gas escaping. Even if methane gas does escape, it is still unclear how much of this could be oxidized in the overlying ocean. Models of the global inventory of hydrates and trapped methane bubbles suggest that a global 3( degrees )C warming could release between 35 and 940 GtC, which could add up to an additional 0.5( degrees )C to global warming. The destabilization of gas hydrate reserves in permafrost areas is more certain as climate models predict that high-latitude regions will be disproportionately affected by global warming with temperature increases of over 12( degrees )C predicted for much of North America and Northern Asia. Our current estimates of gas hydrate storage in the Arctic region are, however, extremely poor and non-existent for Antarctica. The shrinking of both the Greenland and Antarctic ice sheets in response to regional warming may also lead to destabilization of gas hydrates. As ice sheets shrink, the weight removed allows the coastal region and adjacent continental slope to rise through isostacy. This removal of hydrostatic pressure could destabilize gas hydrates, leading to massive slope failure, and may increase the risk of

  3. Novel hydrogen hydrate structures under pressure.

    Science.gov (United States)

    Qian, Guang-Rui; Lyakhov, Andriy O; Zhu, Qiang; Oganov, Artem R; Dong, Xiao

    2014-01-01

    Gas hydrates are systems of prime importance. In particular, hydrogen hydrates are potential materials of icy satellites and comets, and may be used for hydrogen storage. We explore the H₂O-H₂ system at pressures in the range 0-100 GPa with ab initio variable-composition evolutionary simulations. According to our calculation and previous experiments, the H₂O-H₂ system undergoes a series of transformations with pressure, and adopts the known open-network clathrate structures (sII, C₀), dense "filled ice" structures (C₁, C₂) and two novel hydrate phases. One of these is based on the hexagonal ice framework and has the same H₂O:H₂ ratio (2:1) as the C₀ phase at low pressures and similar enthalpy (we name this phase Ih-C₀). The other newly predicted hydrate phase has a 1:2 H₂O:H₂ ratio and structure based on cubic ice. This phase (which we name C₃) is predicted to be thermodynamically stable above 38 GPa when including van der Waals interactions and zero-point vibrational energy, and explains previously mysterious experimental X-ray diffraction and Raman measurements. This is the hydrogen-richest hydrate and this phase has a remarkable gravimetric density (18 wt.%) of easily extractable hydrogen.

  4. First-principles elasticity of monocarboaluminate hydrates

    KAUST Repository

    Moon, J.

    2014-07-01

    The elasticity of monocarboaluminate hydrates, 3CaO·Al2O3·CaCO3·xH2O (x = 11 or 8), has been investigated by first-principles calculations. Previous experimental study revealed that the fully hydrated monocarboaluminate (x = 11) exhibits exceptionally low compressibility compared to other reported calcium aluminate hydrates. This stiff hydration product can contribute to the strength of concrete made with Portland cements containing calcium carbonates. In this study, full elastic tensors and mechanical properties of the crystal structures with different water contents (x = 11 or 8) are computed by first-principles methods based on density functional theory. The results indicate that the compressibility of monocarboaluminate is highly dependent on the water content in the interlayer region. The structure also becomes more isotropic with the addition of water molecules in this region. Since the monocarboaluminate is a key hydration product of limestone added cement, elasticity of the crystal is important to understand its mechanical impact on concrete. Besides, it is put forth that this theoretical calculation will be useful in predicting the elastic properties of other complex cementitous materials and the influence of ion exchange on compressibility.

  5. Stability evaluation of hydrate-bearing sediments during thermally-driven hydrate dissociation

    Science.gov (United States)

    Kwon, T.; Cho, G.; Santamarina, J.; Kim, H.; Lee, J.

    2009-12-01

    Hydrate-bearing sediments may destabilize spontaneously as part of geological processes, unavoidably during petroleum drilling/production operations, or intentionally as part of gas extraction from the hydrate itself. In all cases, high pore fluid pressure generation is anticipated during hydrate dissociation. This study examined how thermal changes destabilize gas hydrate-bearing sediments. First, an analytical formulation was derived for predicting fluid pressure evolution in hydrate-bearing sediments subjected to thermal stimulation without mass transfer. The formulation captures the self-preservation behavior, calculates the hydrate and free gas quantities during dissociation, considering effective stress-controlled sediment compressibility and gas solubility in aqueous phase. Pore fluid pressure generation is proportional to the initial hydrate fraction and the sediment bulk stiffness; is inversely proportional to the initial gas fraction and gas solubility; and is limited by changes in effective stress that cause the failure of the sediment. Second, the analytical formulation for hydrate dissociation was incorporated as a user-defined function into a verified finite difference code (FLAC2D). The underlying physical processes of hydrate-bearing sediments, including hydrate dissociation, self-preservation, pore pressure evolution, gas dissolution, and sediment volume expansion, were coupled with the thermal conduction, pore fluid flow, and mechanical response of sediments. We conducted the simulations for a duration of 20 years, assuming a constant-temperature wellbore transferred heat to the surrounding hydrate-bearing sediments, resulting in dissociation of methane hydrate in the well vicinity. The model predicted dissociation-induced excess pore fluid pressures which resulted in a large volume expansion and plastic deformation of the sediments. Furthermore, when the critical stress was reached, localized shear failure of the sediment around the borehole was

  6. Methane hydrates in nature - Current knowledge and challenges

    Science.gov (United States)

    Collett, Timothy S.

    2014-01-01

    Recognizing the importance of methane hydrate research and the need for a coordinated effort, the United States Congress enacted the Methane Hydrate Research and Development Act of 2000. At the same time, the Ministry of International Trade and Industry in Japan launched a research program to develop plans for a methane hydrate exploratory drilling project in the Nankai Trough. India, China, the Republic of Korea, and other nations also have established large methane hydrate research and development programs. Government-funded scientific research drilling expeditions and production test studies have provided a wealth of information on the occurrence of methane hydrates in nature. Numerous studies have shown that the amount of gas stored as methane hydrates in the world may exceed the volume of known organic carbon sources. However, methane hydrates represent both a scientific and technical challenge, and much remains to be learned about their characteristics and occurrence in nature. Methane hydrate research in recent years has mostly focused on: (1) documenting the geologic parameters that control the occurrence and stability of methane hydrates in nature, (2) assessing the volume of natural gas stored within various methane hydrate accumulations, (3) analyzing the production response and characteristics of methane hydrates, (4) identifying and predicting natural and induced environmental and climate impacts of natural methane hydrates, (5) analyzing the methane hydrate role as a geohazard, (6) establishing the means to detect and characterize methane hydrate accumulations using geologic and geophysical data, and (7) establishing the thermodynamic phase equilibrium properties of methane hydrates as a function of temperature, pressure, and gas composition. The U.S. Department of Energy (DOE) and the Consortium for Ocean Leadership (COL) combined their efforts in 2012 to assess the contributions that scientific drilling has made and could continue to make to advance

  7. Aggregation of Calcium Silicate Hydrate Nanoplatelets.

    Science.gov (United States)

    Delhorme, Maxime; Labbez, Christophe; Turesson, Martin; Lesniewska, Eric; Woodward, Cliff E; Jönsson, Bo

    2016-03-01

    We study the aggregation of calcium silicate hydrate nanoplatelets on a surface by means of Monte Carlo and molecular dynamics simulations at thermodynamic equilibrium. Calcium silicate hydrate (C-S-H) is the main component formed in cement and is responsible for the strength of the material. The hydrate is formed in early cement paste and grows to form platelets on the nanoscale, which aggregate either on dissolving cement particles or on auxiliary particles. The general result is that the experimentally observed variations in these dynamic processes generically called growth can be rationalized from interaction free energies, that is, from pure thermodynamic arguments. We further show that the surface charge density of the particles determines the aggregate structures formed by C-S-H and thus their growth modes. PMID:26859614

  8. Relaxation mechanism of the hydrated electron.

    Science.gov (United States)

    Elkins, Madeline H; Williams, Holly L; Shreve, Alexander T; Neumark, Daniel M

    2013-12-20

    The relaxation dynamics of the photoexcited hydrated electron have been subject to conflicting interpretations. Here, we report time-resolved photoelectron spectra of hydrated electrons in a liquid microjet with the aim of clarifying ambiguities from previous experiments. A sequence of three ultrashort laser pulses (~100 femtosecond duration) successively created hydrated electrons by charge-transfer-to-solvent excitation of dissolved anions, electronically excited these electrons via the s→p transition, and then ejected them into vacuum. Two distinct transient signals were observed. One was assigned to the initially excited p-state with a lifetime of ~75 femtoseconds, and the other, with a lifetime of ~400 femtoseconds, was attributed to s-state electrons just after internal conversion in a nonequilibrated solvent environment. These assignments support the nonadiabatic relaxation model. PMID:24357314

  9. Propane hydrate nucleation: Experimental investigation and correlation

    DEFF Research Database (Denmark)

    Jensen, Lars; Thomsen, Kaj; von Solms, Nicolas

    2008-01-01

    In this work the nucleation kinetics of propane gas hydrate has been investigated experimentally using a stirred batch reactor. The experiments have been performed isothermally recording the pressure as a function of time. Experiments were conducted at different stirring rates, but in the same...... supersaturation region. The experiments showed that the gas dissolution rate rather than the induction time of propane hydrate is influenced by a change in agitation. This was especially valid at high stirring rates when the water surface was severely disturbed.Addition of polyvinylpyrrolidone (PVP...... the presence of additives. In most cases reasonable agreement between the data and the model could be obtained. The results revealed that especially the effective surface energy between propane hydrate and water is likely to change when the stirring rate varies from very high to low. The prolongation...

  10. Hydration shells exchange charge with their protein

    DEFF Research Database (Denmark)

    Abitan, Haim; Lindgård, Per-Anker; Nielsen, Bjørn Gilbert;

    2010-01-01

    Investigation of the interaction between a protein and its hydration shells is an experimental and theoretical challenge. Here, we used ultrasonic pressure waves in aqueous solutions of a protein to explore the conformational states of the protein and its interaction with its hydration shells....... In our experiments, the amplitude of an ultrasonic pressure wave is gradually increased (0–20 atm) while we simultaneously measure the Raman spectra from the hydrated protein (β-lactoglobulin and lysozyme). We detected two types of spectral changes: first, up to 70% increase in the intensity...... of the fluorescence background of the Raman spectrum with a typical relaxation time of 30–45 min. Second, we detect changes in the vibrational Raman spectra. To clarify these results we conducted similar experiments with aqueous solutions of amino acids and ethanol. These experiments led us to conclude that, without...

  11. Simulation of Methane Recovery from Gas Hydrates Combined with Storing Carbon Dioxide as Hydrates

    Directory of Open Access Journals (Sweden)

    Georg Janicki

    2011-01-01

    Full Text Available In the medium term, gas hydrate reservoirs in the subsea sediment are intended as deposits for carbon dioxide (CO2 from fossil fuel consumption. This idea is supported by the thermodynamics of CO2 and methane (CH4 hydrates and the fact that CO2 hydrates are more stable than CH4 hydrates in a certain P-T range. The potential of producing methane by depressurization and/or by injecting CO2 is numerically studied in the frame of the SUGAR project. Simulations are performed with the commercial code STARS from CMG and the newly developed code HyReS (hydrate reservoir simulator especially designed for hydrate processing in the subsea sediment. HyReS is a nonisothermal multiphase Darcy flow model combined with thermodynamics and rate kinetics suitable for gas hydrate calculations. Two scenarios are considered: the depressurization of an area 1,000 m in diameter and a one/two-well scenario with CO2 injection. Realistic rates for injection and production are estimated, and limitations of these processes are discussed.

  12. Simulation of subsea gas hydrate exploitation

    Science.gov (United States)

    Janicki, Georg; Schlüter, Stefan; Hennig, Torsten; Deerberg, Görge

    2014-05-01

    The recovery of methane from gas hydrate layers that have been detected in several subsea sediments and permafrost regions around the world is a promising perspective to overcome future shortages in natural gas supply. Being aware that conventional natural gas resources are limited, research is going on to develop technologies for the production of natural gas from such new sources. Thus various research programs have started since the early 1990s in Japan, USA, Canada, India, and Germany to investigate hydrate deposits and develop required technologies. In recent years, intensive research has focussed on the capture and storage of CO2 from combustion processes to reduce climate impact. While different natural or man-made reservoirs like deep aquifers, exhausted oil and gas deposits or other geological formations are considered to store gaseous or liquid CO2, the storage of CO2 as hydrate in former methane hydrate fields is another promising alternative. Due to beneficial stability conditions, methane recovery may be well combined with CO2 storage in the form of hydrates. Regarding technological implementation many problems have to be overcome. Especially mixing, heat and mass transfer in the reservoir are limiting factors causing very long process times. Within the scope of the German research project »SUGAR« different technological approaches for the optimized exploitation of gas hydrate deposits are evaluated and compared by means of dynamic system simulations and analysis. Detailed mathematical models for the most relevant chemical and physical processes are developed. The basic mechanisms of gas hydrate formation/dissociation and heat and mass transport in porous media are considered and implemented into simulation programs. Simulations based on geological field data have been carried out. The studies focus on the potential of gas production from turbidites and their fitness for CO2 storage. The effects occurring during gas production and CO2 storage within

  13. Nanostructure of Calcium Silicate Hydrates in Cements

    KAUST Repository

    Skinner, L. B.

    2010-05-11

    Calcium silicate hydrate (CSH) is the major volume phase in the matrix of Portland cement concrete. Total x-ray scattering measurements with synchrotron x rays on synthetic CSH(I) shows nanocrystalline ordering with a particle diameter of 3.5(5) nm, similar to a size-broadened 1.1 nm tobermorite crystal structure. The CSH component in hydrated tricalcium silicate is found to be similar to CSH(I). Only a slight bend and additional disorder within the CaO sheets is required to explain its nanocrystalline structure. © 2010 The American Physical Society.

  14. Experimental Study of Gas Hydrate Dynamics

    Science.gov (United States)

    Fandino, O.; Ruffine, L.

    2011-12-01

    Important quantities of methane and other gases are trapped below the seafloor and in the permafrost by an ice-like solid, called gas hydrates or clathrate hydrates. The latter is formed when water is mixing with different gases at high pressures and low temperatures. Due to a their possible use as a source of energy [1] or the problematic related to flow assurance failure in pipelines [2] the understanding of their processes of formation/destabilisation of these structures becomes a goal for many laboratories research as well as industries. In this work we present an experimental study on the stochastic behaviour of hydrate formation from a bulk phase. The method used here for the experiments was to repeat several time the same hydrate formation procedure and to notice the different from one experiment to another. A variable-volume type high-pressure apparatus with two sapphire windows was used. This device, already presented by Ruffine et al.[3], allows us to perform both kinetics and phase equilibrium measurements. Three initial pressure conditions were considered here, 5.0 MPa, 7.5 MPa and 10.0 MPa. Hydrates have been formed, then allowed to dissociate by stepwise heating. The memory effect has also been investigated after complete dissociation. It turned out that, although the thermodynamics conditions of formation and/or destabilization were reproducible. An attempt to determine the influence of pressure on the nucleation induction time will be discussed. References 1. Sum, A. K.; Koh, C. A.; Sloan, E. D., Clathrate Hydrates: From Laboratory Science to Engineering Practice. Industrial & Engineering Chemistry Research 2009, 48, 7457-7465. 2. Sloan, E. D., A changing hydrate paradigm-from apprehension to avoidance to risk management. Fluid Phase Equilibria 2005, 228, 67-74. 3. Ruffine, L.; Donval, J. P.; Charlou, J. L.; Cremière, A.; Zehnder, B. H., Experimental study of gas hydrate formation and destabilisation using a novel high-pressure apparatus. Marine

  15. Component analysis of the protein hydration entropy

    Science.gov (United States)

    Chong, Song-Ho; Ham, Sihyun

    2012-05-01

    We report the development of an atomic decomposition method of the protein solvation entropy in water, which allows us to understand global change in the solvation entropy in terms of local changes in protein conformation as well as in hydration structure. This method can be implemented via a combined approach based on molecular dynamics simulation and integral-equation theory of liquids. An illustrative application is made to 42-residue amyloid-beta protein in water. We demonstrate how this method enables one to elucidate the molecular origin for the hydration entropy change upon conformational transitions of protein.

  16. GLASS TRANSITION OF HYDRATED WHEAT GLIADIN POWDERS

    Institute of Scientific and Technical Information of China (English)

    Shao-min Sun; Li Zhao; Yi-hu Song; Qiang Zheng

    2011-01-01

    Modulated-temperature differential scanning calorimetric and dynamic mechanical analyses and dielectric spectroscopy were used to investigate the glass transition of hydrated wheat gliadin powders with moisture absorption ranged from 2.30 db% to 18.21 db%. Glass transition temperature (Tg) of dry wheat gliadin was estimated according to the GordonTaylor equation. Structural heterogeneity at high degrees of hydration was revealed in dielectric temperature and frequency spectra. The activation energies (Ea) of the two relaxations were calculated from Arrhenius equation.

  17. [Oral hydration with rehydration salts in appendectomized patients].

    Science.gov (United States)

    Azabache Puente, W; Johanson Arias, L

    1992-01-01

    A randomised prospective study of 80 patients to demonstrate if oral hydration with rehydratant salts is as effective as the parenteral infusion for the hydration of patients immediately after appendectomy was performed. The tolerance and conditions of hydration were excellent with 92.5% and 87.5% respectively with oral hydration and with parenteral hydration (p > 0.05). The use of Metronidazole orally with Gentamycetin intramuscular or complication such a wound infection did not influence the hospital stay. With oral hydration, apatite returned sooner, (p saving of cost, saving of time en administration of fluids and shorter hospital stay in the patient with oral hydration than with the parenteral hydration group. PMID:1340245

  18. Geo-scientific investigations of gas-hydrates in India

    Digital Repository Service at National Institute of Oceanography (India)

    Sain, K.; Gupta, H.; Mazumdar, A.; Bhaumik, A.K.; Bhowmick, P.K.

    gradient, and geological, geophysical and microbiological studies indicate that shallow sediments in deep water regions are good hosts for gas-hydrates. First, we have prepared the gas-hydrates stability thickness map along the Indian margin, which provides...

  19. Gas hydrate of Lake Baikal: Discovery and varieties

    Science.gov (United States)

    Khlystov, Oleg; De Batist, Marc; Shoji, Hitoshi; Hachikubo, Akihiro; Nishio, Shinya; Naudts, Lieven; Poort, Jeffrey; Khabuev, Andrey; Belousov, Oleg; Manakov, Andrey; Kalmychkov, Gennаdy

    2013-01-01

    This paper summarizes the results of recent gas-hydrate studies in Lake Baikal, the only fresh-water lake in the world containing gas hydrates in its sedimentary infill. We provide a historical overview of the different investigations and discoveries and highlight some recent breakthroughs in our understanding of the Baikal hydrate system. So far, 21 sites of gas hydrate occurrence have been discovered. Gas hydrates are of structures I and II, which are of thermogenic, microbial, and mixed origin. At the 15 sites, gas hydrates were found in mud volcanoes, and the rest six - near gas discharges. Additionally, depending on type of discharge and gas hydrate structure, they were visually different. Investigations using MIR submersibles allowed finding of gas hydrates at the bottom surface of Lake Baikal at the three sites.

  20. A new geopolymeric binder from hydrated-carbonated cement

    OpenAIRE

    Paya Bernabeu, Jorge Juan; Borrachero Rosado, María Victoria; Monzó Balbuena, José Mª; Soriano Martinez, Lourdes; Mitsuuchi Tashima, Mauro

    2012-01-01

    This paper evaluates the use of hydrated Portland cement as the raw material in the production of geopolymers. The silicon and aluminium oxides needed for the geopolymerization process were produced by the carbonation of hydrated Portland cement, which transforms CSH and CAH (Portland cement hydrates) into silica and alumina gels. Hydrated-carbonated Portland cement was alkali activated with a NaOH/waterglass solution. Pastes and mortars were prepared, and micro-structural and mechanical prop...

  1. Enzyme Activity and Flexibility at Very Low Hydration

    OpenAIRE

    Kurkal, V.; Daniel, R M; Finney, John L.; Tehei, M.; Dunn, R. V.; Jeremy C Smith

    2005-01-01

    Recent measurements have demonstrated enzyme activity at hydrations as low as 3%. This raises the question of whether hydration-induced enzyme flexibility is important for activity. Here, to address this, picosecond dynamic neutron scattering experiments are performed on pig liver esterase powders at 0%, 3%, 12%, and 50% hydration by weight and at temperatures ranging from 120 to 300 K. At all temperatures and hydrations, significant quasielastic scattering intensity is found in the protein, ...

  2. Gas hydrate occurrence and Morpho-structures along Chilean margin

    OpenAIRE

    Vargas Cordero, Ivan De La Cruz

    2009-01-01

    During the last decades, the scientific community spent many efforts to study the gas hydrates in oceanic and permafrost environments. In fact, the gas hydrate occurrence has a global significance because of the potential energy resource represented by the large amount of hydrocarbon trapped in the hydrate phase. Moreover, it may play a role in global climate change, and it is also study because of the hazard that accumulations of gas hydrate may cause to drilling and seabed installations. In...

  3. Application of various water soluble polymers in gas hydrate inhibition

    DEFF Research Database (Denmark)

    Kamal, Muhammad Shahzad; Hussein, Ibnelwaleed A.; Sultan, Abdullah S.;

    2016-01-01

    Formation of hydrates in gas transmission lines due to high pressures and low temperatures is a serious problem in the oil and gas industry with potential hazards and/or economic losses. Kinetic hydrate inhibitors are water soluble polymeric compounds that prevent or delay hydrate formation. This...

  4. Small angle X-ray scattering from hydrating tricalcium silicate

    International Nuclear Information System (INIS)

    The small-angle X-ray scattering technique was used to study the structural evolution of hydrated tricalcium silicate at room temperature. The changes in specific area of the associated porosity and the evolution of density fluctuations in the solid hydrated phase were deduced from the scattering data. A correlation of these variations with the hydration mechanism is tried. (Author)

  5. Hydrate bearing clayey sediments: Formation and gas production concepts

    KAUST Repository

    Jang, Jaewon

    2016-06-20

    Hydro-thermo-chemo and mechanically coupled processes determine hydrate morphology and control gas production from hydrate-bearing sediments. Force balance, together with mass and energy conservation analyses anchored in published data provide robust asymptotic solutions that reflect governing processes in hydrate systems. Results demonstrate that hydrate segregation in clayey sediments results in a two-material system whereby hydrate lenses are surrounded by hydrate-free water-saturated clay. Hydrate saturation can reach ≈2% by concentrating the excess dissolved gas in the pore water and ≈20% from metabolizable carbon. Higher hydrate saturations are often found in natural sediments and imply methane transport by advection or diffusion processes. Hydrate dissociation is a strongly endothermic event; the available latent heat in a reservoir can sustain significant hydrate dissociation without triggering ice formation during depressurization. The volume of hydrate expands 2-to-4 times upon dissociation or CO2single bondCH4 replacement. Volume expansion can be controlled to maintain lenses open and to create new open mode discontinuities that favor gas recovery. Pore size is the most critical sediment parameter for hydrate formation and gas recovery and is controlled by the smallest grains in a sediment. Therefore any characterization must carefully consider the amount of fines and their associated mineralogy.

  6. Elastic properties of gas hydrate-bearing sediments

    Science.gov (United States)

    Lee, M.W.; Collett, T.S.

    2001-01-01

    Downhole-measured compressional- and shear-wave velocities acquired in the Mallik 2L-38 gas hydrate research well, northwestern Canada, reveal that the dominant effect of gas hydrate on the elastic properties of gas hydrate-bearing sediments is as a pore-filling constituent. As opposed to high elastic velocities predicted from a cementation theory, whereby a small amount of gas hydrate in the pore space significantly increases the elastic velocities, the velocity increase from gas hydrate saturation in the sediment pore space is small. Both the effective medium theory and a weighted equation predict a slight increase of velocities from gas hydrate concentration, similar to the field-observed velocities; however, the weighted equation more accurately describes the compressional- and shear-wave velocities of gas hydrate-bearing sediments. A decrease of Poisson's ratio with an increase in the gas hydrate concentration is similar to a decrease of Poisson's ratio with a decrease in the sediment porosity. Poisson's ratios greater than 0.33 for gas hydrate-bearing sediments imply the unconsolidated nature of gas hydrate-bearing sediments at this well site. The seismic characteristics of gas hydrate-bearing sediments at this site can be used to compare and evaluate other gas hydrate-bearing sediments in the Arctic.

  7. When proteins are completely hydrated in crystals.

    Science.gov (United States)

    Carugo, Oliviero

    2016-08-01

    In the crystalline state, protein surface patches that do not form crystal packing contacts are exposed to the solvent and one or more layers of hydration water molecules can be observed. It is well known that these water molecules cannot be observed at very low resolution, when the scarcity of experimental information precludes the observation of several parts of the protein molecule, like for example side-chains at the protein surface. On the contrary, more details are observable at high resolution. Here it is shown that it is necessary to reach a resolution of about 1.5-1.6Å to observe a continuous hydration layer at the protein surface. This contrasts previous estimations, which were more tolerant and according to which a resolution of 2.5Å was sufficient to describe at the atomic level the structure of the hydration layer. These results should prove useful in guiding a more rigorous selection of structural data to study protein hydration and in interpreting new crystal structures. PMID:27112977

  8. Foam drilling in natural gas hydrate

    Directory of Open Access Journals (Sweden)

    Wei Na

    2015-01-01

    Full Text Available The key problem of foam drilling in natural gas hydrate is prediction of characteristic parameters of bottom hole. The simulation shows that when the well depth increases, the foam mass number reduces and the pressure increases. At the same depth, pressure in drill string is always higher than annulus. The research findings provide theoretical basis for safety control.

  9. A positron annihilation study of hydrated DNA

    DEFF Research Database (Denmark)

    Warman, J. M.; Eldrup, Morten Mostgaard

    1986-01-01

    Positron annihilation measurements are reported for hydrated DNA as a function of water content and as a function of temperature (20 to -180.degree. C) for samples containing 10 and 50% wt of water. The ortho-positronium mean lifetime and its intensity show distinct variations with the degree...

  10. Alkali binding in hydrated Portland cement paste

    NARCIS (Netherlands)

    Chen, W.; Brouwers, H.J.H.

    2010-01-01

    The alkali-binding capacity of C–S–H in hydrated Portland cement pastes is addressed in this study. The amount of bound alkalis in C–S–H is computed based on the alkali partition theories firstly proposed by Taylor (1987) and later further developed by Brouwers and Van Eijk (2003). Experimental data

  11. Hydration dynamics near a model protein surface

    International Nuclear Information System (INIS)

    The evolution of water dynamics from dilute to very high concentration solutions of a prototypical hydrophobic amino acid with its polar backbone, N-acetyl-leucine-methylamide (NALMA), is studied by quasi-elastic neutron scattering and molecular dynamics simulation for both the completely deuterated and completely hydrogenated leucine monomer. We observe several unexpected features in the dynamics of these biological solutions under ambient conditions. The NALMA dynamics shows evidence of de Gennes narrowing, an indication of coherent long timescale structural relaxation dynamics. The translational water dynamics are analyzed in a first approximation with a jump diffusion model. At the highest solute concentrations, the hydration water dynamics is significantly suppressed and characterized by a long residential time and a slow diffusion coefficient. The analysis of the more dilute concentration solutions takes into account the results of the 2.0M solution as a model of the first hydration shell. Subtracting the first hydration layer based on the 2.0M spectra, the translational diffusion dynamics is still suppressed, although the rotational relaxation time and residential time are converged to bulk-water values. Molecular dynamics analysis shows spatially heterogeneous dynamics at high concentration that becomes homogeneous at more dilute concentrations. We discuss the hydration dynamics results of this model protein system in the context of glassy systems, protein function, and protein-protein interfaces

  12. Anaerobic oxidation of methane above gas hydrates at Hydrate Ridge, NE Pacific Ocean

    DEFF Research Database (Denmark)

    Treude, T.; Boetius, A.; Knittel, K.;

    2003-01-01

    At Hydrate Ridge (HR), Cascadia convergent margin, surface sediments contain massive gas hydrates formed from methane that ascends together with fluids along faults from deeper reservoirs. Anaerobic oxidation of methane (AOM), mediated by a microbial consortium of archaea and sulfate-reducing...... bacteria, generates high concentrations of hydrogen sulfide in the surface sediments. The production of sulfide supports chemosynthetic communities that gain energy from sulfide oxidation. Depending on fluid flow, the surface communities are dominated either by the filamentous sulfur bacteria Beggiatoa...

  13. China's Research on Non-conventional Energy Resources- Gas Hydrate

    Institute of Scientific and Technical Information of China (English)

    Pu Ming; Ma Jianguo

    2002-01-01

    @@ Methane exists in ice-like formations called gas hydrate. Hydrate traps methane molecules inside a cage of frozen water. The magnitude of this previously unknown global storehouse of methane is truly staggering and has raised serious inquiry into the possibility of using methane hydrate as a substitute source of energy for oil and conventional natural gas. According to the estimation by PGC, gas hydrate deposits amount to 7.6 × 1018m3 and contain more than twice as much organic carbon as all the world's coal, oil and non-hydrate natural gas combined.

  14. A method of harvesting gas hydrates from marine sediments

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, H.Q.; Brill, J.P.; Sarica, C. [Tulsa Univ., Tulsa, OK (United States). Dept. of Petroleum Engineering

    2008-07-01

    Methane is known to exist in gas hydrates, but low productivity is expected for gas production from gas hydrates in marine sediments because of the shallow depths, low hydrate concentration, low permeability of the gas hydrate stability zone, lack of driving pressure and the slow melting process. This paper presented a newly developed methane harvesting method which aims to overcome technical barriers, maintain cost and energy efficiencies and minimize safety and environmental concerns. The method is based on the concept of capturing the gas released from hydrate dissociation in the sediments. The captured gases can reform hydrates inside and overhead receiver, which once full, can be lifted to shallow warm water for gas collection. This simple and open production system does not require high pressure and does not involve any flow assurance issues. As such, technical difficulties, safety issues and environmental concerns are minimized. The proposed gas harvesting method makes the best use of the nature of hydrates and the subsea pressure and temperature profiles. It combines many new concepts, including electrically adding heat inside the hydrate rich sediments to release gas, using an overhead receiver to capture the gas, allowing the gas to reform hydrates again in the overhead receiver, and lifting produced hydrates to warm water where it can be released and collected. It was concluded that this newly proposed production system enables the development of massive hydrate production fields on the sea bed with high production rates that are economically viable. 4 refs., 7 figs.

  15. Comparative Assessment of Advanced Gay Hydrate Production Methods

    Energy Technology Data Exchange (ETDEWEB)

    M. D. White; B. P. McGrail; S. K. Wurstner

    2009-06-30

    Displacing natural gas and petroleum with carbon dioxide is a proven technology for producing conventional geologic hydrocarbon reservoirs, and producing additional yields from abandoned or partially produced petroleum reservoirs. Extending this concept to natural gas hydrate production offers the potential to enhance gas hydrate recovery with concomitant permanent geologic sequestration. Numerical simulation was used to assess a suite of carbon dioxide injection techniques for producing gas hydrates from a variety of geologic deposit types. Secondary hydrate formation was found to inhibit contact of the injected CO{sub 2} regardless of injectate phase state, thus diminishing the exchange rate due to pore clogging and hydrate zone bypass of the injected fluids. Additional work is needed to develop methods of artificially introducing high-permeability pathways in gas hydrate zones if injection of CO{sub 2} in either gas, liquid, or micro-emulsion form is to be more effective in enhancing gas hydrate production rates.

  16. Water retention curve for hydrate-bearing sediments

    Science.gov (United States)

    Dai, Sheng; Santamarina, J. Carlos

    2013-11-01

    water retention curve plays a central role in numerical algorithms that model hydrate dissociation in sediments. The determination of the water retention curve for hydrate-bearing sediments faces experimental difficulties, and most studies assume constant water retention curves regardless of hydrate saturation. This study employs network model simulation to investigate the water retention curve for hydrate-bearing sediments. Results show that (1) hydrate in pores shifts the curve to higher capillary pressures and the air entry pressure increases as a power function of hydrate saturation; (2) the air entry pressure is lower in sediments with patchy rather than distributed hydrate, with higher pore size variation and pore connectivity or with lower specimen slenderness along the flow direction; and (3) smaller specimens render higher variance in computed water retention curves, especially at high water saturation Sw > 0.7. Results are relevant to other sediment pore processes such as bioclogging and mineral precipitation.

  17. Natural gas hydrates. Experimental techniques and their applications

    Energy Technology Data Exchange (ETDEWEB)

    Ye, Yuguang; Liu, Changling (eds.) [Qingdao Institute of Marine Geology (China). Gas Hydrate Laboratory

    2013-07-01

    Focuses on gas hydrate experiment in laboratory. Intends to provide practical significant parameters for gas hydrate exploration and exploitation in the oceanic and permafrost environments. Consists of different themes that present up-to-date information on hydrate experiments. ''Natural Gas Hydrates: Experimental Techniques and Their Applications'' attempts to broadly integrate the most recent knowledge in the fields of hydrate experimental techniques in the laboratory. The book examines various experimental techniques in order to provide useful parameters for gas hydrate exploration and exploitation. It provides experimental techniques for gas hydrates, including the detection techniques, the thermo-physical properties, permeability and mechanical properties, geochemical abnormalities, stability and dissociation kinetics, exploitation conditions, as well as modern measurement technologies etc.

  18. Towards a green hydrate inhibitor: imaging antifreeze proteins on clathrates.

    Directory of Open Access Journals (Sweden)

    Raimond Gordienko

    Full Text Available The formation of hydrate plugs in oil and gas pipelines is a serious industrial problem and recently there has been an increased interest in the use of alternative hydrate inhibitors as substitutes for thermodynamic inhibitors like methanol. We show here that antifreeze proteins (AFPs possess the ability to modify structure II (sII tetrahydrofuran (THF hydrate crystal morphologies by adhering to the hydrate surface and inhibiting growth in a similar fashion to the kinetic inhibitor poly-N-vinylpyrrolidone (PVP. The effects of AFPs on the formation and growth rate of high-pressure sII gas mix hydrate demonstrated that AFPs are superior hydrate inhibitors compared to PVP. These results indicate that AFPs may be suitable for the study of new inhibitor systems and represent an important step towards the development of biologically-based hydrate inhibitors.

  19. In-situ gas hydrate hydrate saturation estimated from various well logs at the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope

    Science.gov (United States)

    Lee, M.W.; Collett, T.S.

    2011-01-01

    In 2006, the U.S. Geological Survey (USGS) completed detailed analysis and interpretation of available 2-D and 3-D seismic data and proposed a viable method for identifying sub-permafrost gas hydrate prospects within the gas hydrate stability zone in the Milne Point area of northern Alaska. To validate the predictions of the USGS and to acquire critical reservoir data needed to develop a long-term production testing program, a well was drilled at the Mount Elbert prospect in February, 2007. Numerous well log data and cores were acquired to estimate in-situ gas hydrate saturations and reservoir properties.Gas hydrate saturations were estimated from various well logs such as nuclear magnetic resonance (NMR), P- and S-wave velocity, and electrical resistivity logs along with pore-water salinity. Gas hydrate saturations from the NMR log agree well with those estimated from P- and S-wave velocity data. Because of the low salinity of the connate water and the low formation temperature, the resistivity of connate water is comparable to that of shale. Therefore, the effect of clay should be accounted for to accurately estimate gas hydrate saturations from the resistivity data. Two highly gas hydrate-saturated intervals are identified - an upper ???43 ft zone with an average gas hydrate saturation of 54% and a lower ???53 ft zone with an average gas hydrate saturation of 50%; both zones reach a maximum of about 75% saturation. ?? 2009.

  20. Probing methane hydrate nucleation through the forward flux sampling method.

    Science.gov (United States)

    Bi, Yuanfei; Li, Tianshu

    2014-11-26

    Understanding the nucleation of hydrate is the key to developing effective strategies for controlling methane hydrate formation. Here we present a computational study of methane hydrate nucleation, by combining the forward flux sampling (FFS) method and the coarse-grained water model mW. To facilitate the application of FFS in studying the formation of methane hydrate, we developed an effective order parameter λ on the basis of the topological analysis of the tetrahedral network. The order parameter capitalizes the signature of hydrate structure, i.e., polyhedral cages, and is capable of efficiently distinguishing hydrate from ice and liquid water while allowing the formation of different hydrate phases, i.e., sI, sII, and amorphous. Integration of the order parameter λ with FFS allows explicitly computing hydrate nucleation rates and obtaining an ensemble of nucleation trajectories under conditions where spontaneous hydrate nucleation becomes too slow to occur in direct simulation. The convergence of the obtained hydrate nucleation rate was found to depend crucially on the convergence of the spatial distribution for the spontaneously formed hydrate seeds obtained from the initial sampling of FFS. The validity of the approach is also verified by the agreement between the calculated nucleation rate and that inferred from the direct simulation. Analyzing the obtained large ensemble of hydrate nucleation trajectories, we show hydrate formation at 220 K and 500 bar is initiated by the nucleation events occurring in the vicinity of water-methane interface, and facilitated by a gradual transition from amorphous to crystalline structure. The latter provides the direct support to the proposed two-step nucleation mechanism of methane hydrate. PMID:24849698

  1. Hydration index--a better parameter for explaining small molecule hydration in inhibition of ice recrystallization.

    Science.gov (United States)

    Tam, Roger Y; Ferreira, Sandra S; Czechura, Pawel; Chaytor, Jennifer L; Ben, Robert N

    2008-12-24

    Several simple mono- and disaccharides have been assessed for their ability to inhibit ice recrystallization. Two carbohydrates were found to be effective recrystallization inhibitors. D-galactose (1) was the best monosaccharide and D-melibiose (5) was the most active disaccharide. The ability of each carbohydrate to inhibit ice growth was correlated to its respective hydration number reported in the literature. A hydration number reflects the number of tightly bound water molecules to the carbohydrate and is a function of carbohydrate stereochemistry. It was discovered that using the absolute hydration number of a carbohydrate does not allow one to accurately predict its ability to inhibit ice recrystallization. Consequently, we have defined a hydration index in which the hydration number is divided by the molar volume of the carbohydrate. This new parameter not only takes into account the number of water molecules tightly bound to a carbohydrate but also the size or volume of a particular solute and ultimately the concentration of hydrated water molecules. The hydration index of both mono- and disaccharides correlates well with experimentally measured RI activity. C-Linked derivatives of the monosaccharides appear to have RI activity comparable to that of their O-linked saccharides but a more thorough investigation is required. The relationship between carbohydrate concentration and RI activity was shown to be noncolligative and a 0.022 M solution of D-galactose (1) and C-linked galactose derivative (10) inhibited recrystallization as well as a 3% DMSO solution. The carbohydrates examined in this study did not possess any thermal hysteresis activity (selective depression of freezing point relative to melting point) or dynamic ice shaping. As such, we propose that they are inhibiting recrystallization at the interface between bulk water and the quasi liquid layer (a semiordered interface between ice and bulk water) by disrupting the preordering of water.

  2. Geologic implications of gas hydrates in the offshore of India: results of the National Gas Hydrate Program Expedition 01

    Science.gov (United States)

    Collett, Timothy S.; Boswell, Ray; Cochran, J.R.; Kumar, Pushpendra; Lall, Malcolm; Mazumdar, Aninda; Ramana, Mangipudi Venkata; Ramprasad, Tammisetti; Riedel, Michael; Sain, Kalachand; Sathe, Arun Vasant; Vishwanath, Krishna

    2014-01-01

    The Indian National Gas Hydrate Program Expedition 01 (NGHP-01) is designed to study the occurrence of gas hydrate along the passive continental margin of the Indian Peninsula and in the Andaman convergent margin, with special emphasis on understanding the geologic and geochemical controls on the occurrence of gas hydrate in these two diverse settings. The NGHP-01 expedition established the presence of gas hydrates in the Krishna-Godavari and Mahanadi Basins, and the Andaman Sea. The expedition discovered in the Krishna-Godavari Basin one of the thickest gas hydrate accumulations ever documented, in the Andaman Sea one of the thickest and deepest gas hydrate stability zones in the world, and established the existence of a fully developed gas hydrate petroleum system in all three basins.

  3. Origin and character of gaseous hydrocarbons in the hydrate and non-hydrate charged sediments on the Norway - Svalbard margins

    Energy Technology Data Exchange (ETDEWEB)

    Vaular, Espen Nesheim

    2011-05-15

    Gas incubated in clathrate water-structures, stabilizes the hydrogen bonded substance termed gas hydrate. In the marine environment vast amount of carbon is stored as gas hydrates within the temperature and pressure zone these ice-like structures are stable. Natural gas hydrate mapping and characterization is important basic research that brings about critical knowledge concerning various topics. Natural gas hydrates is a vital part of the carbon cycle, it is a potential energy resource (and thereby a potential climate agent) and it is a potential geo-hazard. One of the goals the GANS initiative aimed at exploring, was the hydrate bearing sediment of the Norway -Svalbard margins, to investigate the character and expansion of natural gas hydrates. Part of the investigation was to define how the gas in the hydrated sediment was produced and where it came from. As a result this thesis addresses the matter of light hydrocarbon characterization and origin in two Norwegian hydrate deposits. On cruises to Vestnesa on the Svalbard margin and to Nyegga in the mid-Norwegian margin, samples of hydrate charged and non-hydrate charged sediments were obtained and analyzed. Through compositional and isotopic analyses the origin of the hydrate bound gas in the fluid escape feature G11 at Nyegga was determined. The hydrate incubated methane is microbial produced as well as parts of the hydrate bound ethane. The compositional analysis in both the Nyegga area and at the Vestnesa Ridge points at thermogenic contributions in the sediment interstitials and pore water. The two hydrate bearing margins show large differences in hydrocarbon content and microbial activity in the pockmarks investigated. The gravity cores from the penetrated pockmark at Vestnesa showed low hydrocarbon content and thus suggest ceased or periodic venting. The fluid flow escape features at Nyegga show large variety of flux rates based on ROV monitoring and headspace analysis of the sediment and pore water. The

  4. Advances in understanding hydration of Portland cement

    Energy Technology Data Exchange (ETDEWEB)

    Scrivener, Karen L., E-mail: Karen.scrivener@epfl.ch [Laboratory of Construction Materials, Ecole Polytechnique Fédérale de Lausanne, 1015 (Switzerland); Juilland, Patrick [Sika Technology AG, Zürich (Switzerland); Monteiro, Paulo J.M. [Department of Civil and Environmental Engineering, University of California at Berkeley (United States)

    2015-12-15

    Progress in understanding hydration is summarized. Evidence supports the geochemistry dissolution theory as an explanation for the induction period, in preference to the inhibiting layer theory. The growth of C–S–H is the principal factor controlling the main heat evolution peak. Electron microscopy indicates that C–S–H “needles” grow from the surface of grains. At the peak, the surface is covered, but deceleration cannot be attributed to diffusion control. The shoulder peak comes from renewed reaction of C{sub 3}A after depletion of sulfate in solution, but release of sulfate absorbed on C–S–H means that ettringite continues to form. After several days space becomes the major factor controlling hydration. The use of new analytical technique is improving our knowledge of the action of superplasticizers and leading to the design of molecules for different applications. Atomistic modeling is becoming a topic of increasing interest. Recent publications in this area are reviewed.

  5. Predicting hydration energies for multivalent ions

    DEFF Research Database (Denmark)

    Andersson, Martin Peter; Stipp, Susan Louise Svane

    2014-01-01

    errors. Our results indicate that quantum chemical calculations combined with COSMO-RS solvent treatment is a reliable method for treating multivalent ions in solution, provided one hydration shell of explicit water molecules is included for metal cations. The accuracy is not high enough to allow...... (TZVP) level. Agreement with experimental data for monovalent and divalent ions is good and shows no significant systematic errors. Predictions are noticeably better than with standard COSMO. The agreement with experimental data for trivalent and tetravalent ions is slightly worse and shows systematic...... absolute predictions of hydration energies but could be used to investigate trends for several ions, thanks to the low computational cost, in particular for ligand exchange reactions....

  6. A statistical mechanical description of biomolecular hydration

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-02-01

    We present an efficient and accurate theoretical description of the structural hydration of biological macromolecules. The hydration of molecules of almost arbitrary size (tRNA, antibody-antigen complexes, photosynthetic reaction centre) can be studied in solution and in the crystal environment. The biomolecular structure obtained from x-ray crystallography, NMR, or modeling is required as input information. The structural arrangement of water molecules near a biomolecular surface is represented by the local water density analogous to the corresponding electron density in an x-ray diffraction experiment. The water-density distribution is approximated in terms of two- and three-particle correlation functions of solute atoms with water using a potentials-of-mean-force expansion.

  7. Experimental techniques for cement hydration studies

    Directory of Open Access Journals (Sweden)

    Andreas Luttge

    2011-10-01

    Full Text Available Cement hydration kinetics is a complex problem of dissolution, nucleation and growth that is still not well understood, particularly in a quantitative way. While cement systems are unique in certain aspects they are also comparable to natural mineral systems. Therefore, geochemistry and particularly the study of mineral dissolution and growth may be able to provide insight and methods that can be utilized in cement hydration research. Here, we review mainly what is not known or what is currently used and applied in a problematic way. Examples are the typical Avrami approach, the application of Transition State Theory (TST to overall reaction kinetics and the problem of reactive surface area. Finally, we suggest an integrated approach that combines vertical scanning interferometry (VSI with other sophisticated analytical techniques such as atomic force microscopy (AFM and theoretical model calculations based on a stochastic treatment.

  8. A Proposed Unified Theory of Hydrated Asteroids

    Science.gov (United States)

    Rivkin, Andrew S.

    2016-10-01

    The last decade has seen tremendous growth in the study of hydrated and hydroxylated minerals (hereafter simply called "hydrated minerals") on asteroids. Several workers have used absorptions in the 3-µm region and a correlated absorption near 0.7 µm to determine not only the presence or absence of these minerals but gain insight into the compositions of asteroid surfaces. Spectra of hundreds of asteroids have been measured and published or presented at meetings, and we are in a position to use these newer datasets to globally assess the patterns and relationships we see, as previously done by Jones et al. (1990) and Takir et al. (2012). There are several points to be addressed by any such assessment. Several different band shapes are seen in the 3-µm region, only one of which is seen in the hydrated meteorites in our collections. However, each of the main 3-µm band shapes is represented among parent bodies of collisional families. There seems to be little correlation in general between asteroid spectral class and 3-µm band shape, save for the Ch meteorites which are overwhelmingly likely to share the same band shape as the CM meteorites. Ceres has an unusual but not unique band shape, which has thus far only been found on the largest asteroids. I will present an outline scenario for the formation and evolution of hydrated asteroids, where aqueous alteration serves to lithify some objects while other objects remain unlithified and still others differentiate and suffer collisional modification. While some details will no doubt be altered to account for better or new information, this scenario is offered as a starting point for discussion.

  9. Bioimpedance in medicine: Measuring hydration influence

    Science.gov (United States)

    Hlubik, J.; Hlubik, P.; Lhotska, L.

    2010-04-01

    The aim of the paper is to present results of our ongoing research focused on the influence of body hydration on the body impedance measurements and also on the influence of the frequency used for the measurement. The question is why to measure human body composition and if these values have beneficial results. First goal of the work deals with a question of measuring human body composition. The performed measurements showed certain influence which must be verified by repeated experiments.

  10. Serrano charged up for hydrates battle

    Energy Technology Data Exchange (ETDEWEB)

    Flatern, R. von

    2001-07-01

    The plugging of pipelines by paraffin and hydrate formations is an obstacle still to be overcome in the transportation of gases in deep cold water. However, a new flow assurance technique is soon to be installed in Shell's Serrano and Oregano fields in the Gulf of Mexico and this is expected to eventually impact on the entire offshore industry: it is this development which is discussed. The system uses electricity to heat the pipelines.

  11. CO₂ processing and hydration of fruit and vegetable tissues by clathrate hydrate formation.

    Science.gov (United States)

    Takeya, Satoshi; Nakano, Kohei; Thammawong, Manasikan; Umeda, Hiroki; Yoneyama, Akio; Takeda, Tohoru; Hyodo, Kazuyuki; Matsuo, Seiji

    2016-08-15

    CO2 hydrate can be used to preserve fresh fruits and vegetables, and its application could contribute to the processing of carbonated frozen food. We investigated water transformation in the frozen tissue of fresh grape samples upon CO2 treatment at 2-3 MPa and 3°C for up to 46 h. Frozen fresh bean, radish, eggplant and cucumber samples were also investigated for comparison. X-ray diffraction indicated that after undergoing CO2 treatment for several hours, structure I CO2 hydrate formed within the grape tissue. Phase-contrast X-ray imaging using the diffraction-enhanced imaging technique revealed the presence of CO2 hydrate within the intercellular spaces of these tissues. The carbonated produce became effervescent because of the dissociation of CO2 hydrate through the intercellular space, especially above the melting point of ice. In addition, suppressed metabolic activity resulting from CO2 hydrate formation, which inhibits water and nutrient transport through intercellular space, can be expected. PMID:27006222

  12. Silicate anion structural change in calcium silicate hydrate gel on dissolution of hydrated cement

    International Nuclear Information System (INIS)

    High pH conditions of aqueous solutions in a radioactive waste repository can be brought about by dissolution of cementitious materials. In order to clarify the mechanisms involved in maintaining this high pH for long time, we investigated the dissolution phenomena of OPC hydrate. In the present research, leaching tests on powdered cement hydrates were conducted by changing the ratio of mass of leaching water to mass of OPC hydrate (liquid/solid ratio) from 10 - 2,000 (wt/wt). Ordinary Portland Cement hydrate was contacted with deionized water and placed in a sealed bottle. After a predetermined period, the solid was separated from the solution. From the results of XRD analysis on the solid phase and the Ca concentration in the aqueous phase, it was confirmed that Ca(OH)2 was preferentially dissolved when the liquid/solid ratio was 10 or 100 (wt/wt), and that C-S-H gel as well as Ca(OH)2 were dissolved when the liquid/solid ratio was 500 (wt/wt) or larger. 29Si-NMR results showed that the silicate anion chain of the C-S-H gel became longer when the liquid/solid ratio was 500 (wt/wt) or greater. This indicates that leaching of OPC hydrate results in a structural change of C-S-H gel. (author)

  13. Terahertz spectroscopy of concrete for evaluating the critical hydration level

    Science.gov (United States)

    Dash, Jyotirmayee; Ray, Shaumik; Nallappan, Kathirvel; Sasmal, Saptarshi; Pesala, Bala

    2014-03-01

    Concrete, a mixture of cement, coarse aggregate, sand and filler material (if any), is widely used in the construction industry. Cement, mainly composed of Tricalcium Silicate (C3S) and Dicalcium Silicate (C2S) reacts readily with water, a process known as hydration. The hydration process forms a solid material known as hardened cement paste which is mainly composed of Calcium Silicate Hydrate (C-S-H), Calcium Hydroxide and Calcium Carbonate. To quantify the critical hydration level, an accurate and fast technique is highly desired. However, in conventional XRD technique, the peaks of the constituents of anhydrated and hydrated cement cannot be resolved properly, where as Mid-infrared (MIR) spectroscopy has low penetration depth and hence cannot be used to determine the hydration level of thicker concrete samples easily. Further, MIR spectroscopy cannot be used to effectively track the formation of Calcium Hydroxide, a key by-product during the hydration process. This paper describes a promising approach to quantify the hydration dynamics of cement using Terahertz (THz) spectroscopy. This technique has been employed to track the time dependent reaction mechanism of the key constituents of cement that react with water and form the products in the hydrated cement, viz., C-S-H, Calcium Hydroxide and Calcium Carbonate. This study helps in providing an improved understanding on the hydration kinetics of cement and also to optimise the physio-mechanical characteristics of concrete.

  14. Coupled THCM Modeling of Gas Hydrate Bearing Sediments

    Science.gov (United States)

    Sanchez, M. J.; Gai, X., Sr.; Shastri, A.; Santamarina, J. C.

    2014-12-01

    Gas hydrates are crystalline clathrate compounds made of water and a low molecular gas, like methane. Gas hydrates are generally present in oil-producing areas and in permafrost regions. Methane hydrate deposits can lead to large-scale submarine slope failures, blowouts, platform foundation failures, and borehole instability. Gas hydrates constitute also an attractive source of energy as they are estimated to contain very large reserves of methane. Hydrate formation, dissociation and methane production from hydrate bearing sediments are coupled Thermo-Hydro-Mechanical (THM) processes that involve, amongst other, exothermic formation and endothermic dissociation of hydrate and ice phases, mixed fluid flow and large changes in fluid pressure. A comprehensive THM formulation is briefly presented here. Momentum balance, mass balance and energy balance equations take into consideration the interaction among all phases (i.e. solid, liquid, gas, hydrates and ice) and mechanical equilibrium. Constitutive equations describe the intrinsic THM behavior of the sediment. Simulation results conducted for hydrate bearing sediments subjected to boundary conditions highlight the complex interaction among THM processes in hydrate bearing sediments.

  15. Hydration process in Portland cement blended with activated coal gangue

    Institute of Scientific and Technical Information of China (English)

    Xian-ping LIU; Pei-ming WANG; Min-ju DING

    2011-01-01

    This paper deals with the hydration of a blend of Portland cement and activated coal gangue in order to determine the relationship between the degree of hydration and compressive strength development.The hydration process was investigated by various means:isothermal calorimetry,thermal analysis,non-cvaporable water measurement,and X-ray diffraction analysis.The results show that the activated coal gangue is a pozzolanic material that contributes to the hydration of the cement blend.The pozzolanic reaction occurs over a period of between 7 and 90 d,consuming portlandite and forming both crystal hydrates and ill-crystallized calcium silicate hydrates.These hydrates are similar to those found in pure Portland cement.The results show that if activated coal gangue is substituted for cement at up to 30% (w/w),it does not significantly affect the final compressive strength of the blend.A long-term compressive strength improvement can in fact be achieved by using activated coal gangue as a supplementary cementing material.The relationship between compressive strength and degree of hydration for both pure Portland cement and blended cement can be described with the same equation.However,the parameters are different since blended cement produces fewer calcium silicate hydrates than pure Portland cement at the same degree of hydration.

  16. Effect of Gemini-type surfactant on methane hydrate formation

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, K.E.; Park, J.M.; Kim, C.U.; Chae, H.J.; Jeong, S.Y. [Korea Research Inst. of Chemical Technology, Jang-Dong, Yuseong-Gu, Daejeon (Korea, Republic of)

    2008-07-01

    Natural gas hydrates are formed from water and natural gas molecules at particular temperatures and pressures that become ice-like inclusion compounds. Gas hydrates offer several benefits such as energy resource potential and high storage capacity of natural gas in the form of hydrates. However, the application of natural gas hydrates has been deterred by its low formation rate and low conversion ratio of water into hydrate resulting in low actual storage capacity. This paper presented an experimental study to determine the effect of adding a novel Gemini-type surfactant on methane hydrate formation. The experimental study was described with reference to the properties of prepared diols and properties of prepared disulfonates. Gemini surfactant is the family of surfactant molecules possessing more than one hydrophobic tail and hydrophilic head group. They generally have better surface-active properties than conventional surfactants of equal chain length. The paper presented the results of the study in terms of the reactions of diols with propane sultone; storage capacity of hydrate formed with and without surfactant; and methane hydrate formation with and without disulfonate. It was concluded that the methane hydrate formation was accelerated by the addition of novel anionic Gemini-type surfactants and that hydrate formation was influenced by the surfactant concentration and alkyl chain length. For a given concentration, the surfactant with the highest chain length demonstrated the highest formation rate and storage capacity. 5 refs., 3 tabs., 4 figs.

  17. Ethical issues in artificial nutrition and hydration.

    Science.gov (United States)

    Fine, Robert L

    2006-04-01

    From the time of Hippocrates, approximately 2500 years ago, medical ethics has been seen as an essential complement to medical science in pursuit of the healing art of medicine. This is no less true today, not only for physicians but also for other essential professionals involved in patient care, including clinical nutrition support practitioners. One aspect of medical ethics that the clinical nutritionist must face involves decisions to provide, withhold, or withdraw artificial nutrition and hydration. Such a decision is not only technical but often has a strong moral component as well. Although it is the physician who writes any such order, the clinical nutritionist as fellow professional should be a part not only of the scientific aspects of the order but of the moral discourse leading to such an order and may certainly be involved in counseling physicians, other healthcare providers, patients, and families alike. This paper is intended to give the clinical nutritionist a familiarity with the discipline of medical ethics and its proper relationship to medical science, politics, and law. This review will then offer a more specific analysis of the ethical aspects of decisions to initiate, withhold, or withdraw artificial nutrition and hydration (ANH) and offer particular commentary on the ethically significant pronouncements of Pope John Paul II in March of 2004 related to vegetative patients and artificial or "assisted" nutrition and hydration. PMID:16556921

  18. Intermolecular Hydrogen Transfer in Isobutane Hydrate

    Directory of Open Access Journals (Sweden)

    Takeshi Sugahara

    2012-05-01

    Full Text Available Electron spin resonance (ESR spectra of butyl radicals induced with γ-ray irradiation in the simple isobutane (2-methylpropane hydrate (prepared with deuterated water were investigated. Isothermal annealing results of the γ-ray-irradiated isobutane hydrate reveal that the isobutyl radical in a large cage withdraws a hydrogen atom from the isobutane molecule through shared hexagonal-faces of adjacent large cages. During this “hydrogen picking” process, the isobutyl radical is apparently transformed into a tert-butyl radical, while the sum of isobutyl and tert-butyl radicals remains constant. The apparent transformation from isobutyl to tert-butyl radicals is an irreversible first-order reaction and the activation energy was estimated to be 35 ± 3 kJ/mol, which was in agreement with the activation energy (39 ± 5 kJ/mol of hydrogen picking in the γ-ray-irradiated propane hydrate with deuterated water.

  19. Impact of Compound Hydrate Dynamics on Phase Boundary Changes

    Science.gov (United States)

    Osegovic, J. P.; Max, M. D.

    2006-12-01

    Compound hydrate reactions are affected by the local concentration of hydrate forming materials (HFM). The relationship between HFM composition and the phase boundary is as significant as temperature and pressure. Selective uptake and sequestration of preferred hydrate formers (PF) has wide ranging implications for the state and potential use of natural hydrate formation, including impact on climate. Rising mineralizing fluids of hydrate formers (such as those that occur on Earth and are postulated to exist elsewhere in the solar system) will sequester PF before methane, resulting in a positive relationship between depth and BTU content as ethane and propane are removed before methane. In industrial settings the role of preferred formers can separate gases. When depressurizing gas hydrate to release the stored gas, the hydrate initial composition will set the decomposition phase boundary because the supporting solution takes on the composition of the hydrate phase. In other settings where hydrate is formed, transported, and then dissociated, similar effects can control the process. The behavior of compound hydrate systems can primarily fit into three categories: 1) In classically closed systems, all the material that can form hydrate is isolated, such as in a sealed laboratory vessel. In such systems, formation and decomposition are reversible processes with observed hysteresis related to mass or heat transfer limitations, or the order and magnitude in which individual hydrate forming gases are taken up from the mixture and subsequently released. 2) Kinetically closed systems are exposed to a solution mass flow across a hydrate mass. These systems can have multiple P-T phase boundaries based on the local conditions at each face of the hydrate mass. A portion of hydrate that is exposed to fresh mineralizing solution will contain more preferred hydrate formers than another portion that is exposed to a partially depleted solution. Examples of kinetically closed

  20. Development of Alaskan gas hydrate resources. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Kamath, V.A.; Sharma, G.D.; Patil, S.L.

    1991-06-01

    The research undertaken in this project pertains to study of various techniques for production of natural gas from Alaskan gas hydrates such as, depressurization, injection of hot water, steam, brine, methanol and ethylene glycol solutions through experimental investigation of decomposition characteristics of hydrate cores. An experimental study has been conducted to measure the effective gas permeability changes as hydrates form in the sandpack and the results have been used to determine the reduction in the effective gas permeability of the sandpack as a function of hydrate saturation. A user friendly, interactive, menu-driven, numerical difference simulator has been developed to model the dissociation of natural gas hydrates in porous media with variable thermal properties. A numerical, finite element simulator has been developed to model the dissociation of hydrates during hot water injection process.

  1. Focus on the Development of Natural Gas Hydrate in China

    Directory of Open Access Journals (Sweden)

    Zhongfu Tan

    2016-05-01

    Full Text Available Natural gas hydrate, also known as combustible ice, and mainly composed of methane, is identified as a potential clean energy for the 21st century. Due to its large reserves, gas hydrate can ease problems caused by energy resource shortage and has gained attention around the world. In this paper, we focus on the exploration and development of gas hydrate as well as discussing its status and future development trend in China and abroad. We then analyze its opportunities and challenges in China from four aspects, resource, technology, economy and policy, with five forces model and Politics Economics Society Technology method. The results show China has abundance gas hydrate resource; however, backward technologies and inadequate investment have seriously hindered the future development of gas hydrate; thus, China should establish relevant cooperation framework and intuitional arrangement to attract more investment as well as breaking through technical difficulties to commercialization gas hydrate as soon as possible.

  2. Enzyme hydration, activity and flexibility : A neutron scattering approach

    Energy Technology Data Exchange (ETDEWEB)

    Kurkal-Siebert, V [University of Heidelberg; Finney, J.L. [University College, London; Daniel, R. M. [University of Waikato, New Zealand; Smith, Jeremy C [ORNL

    2006-01-01

    Recent measurements have demonstrated enzyme activity at hydrations as low as 3%. The question of whether the hydration-induced enzyme flexibility is important for activity is addressed by performing picosecond dynamic neutron scattering experiments on pig liver esterase powders at various temperatures as well as solutions. At all temperatures and hydrations investigated here, significant quasielastic scattering intensity is found in the protein, indicating the presence of anharmonic, diffusive motion. As the hydration increases a temperature-dependent dynamical transition appears and strengthens involving additional diffusive motion. At low temperature, increasing hydration resulted in lower flexibility of the enzyme. At higher temperatures, systems containing sufficient number of water molecules interacting with the protein exhibit increased flexibility. The implication of these results is that, although the additional hydration-induced diffusive motion and flexibility at high temperatures in the enzyme detected here may be related to increased activity, they are not required for the enzyme to function.

  3. STUDY FOR NATURAL GAS HYDRATE CONVERSED FROM ICE

    Institute of Scientific and Technical Information of China (English)

    WANG Shengjie; SHEN Jiandong; HAO Miaoli; LIU Furong

    2003-01-01

    Natural gas hydrates are crystalline clathrate compounds composed of water and gases of small molecular diameters that can be used for storage and transport of natural gas as a novel method. In the paper a series of experiments of aspects and kinetics for hydrate formed from natural gas and ice were carried out on the industrial small scale production apparatus. The experimental results show that formation conditions of hydrate conversed from ice are independent of induction time, and bigger degrees of supersaturation and supercooling improved the driving force and advanced the hydrate formation.Superpressure is also favorable for ice particle conversion to hydrate. In addition, it was found there have an optimal reaction time during hydrate formation.

  4. Octa-coordination and the hydrated Ba2+(aq) ion

    CERN Document Server

    Chaudhari, Mangesh I; Rempe, Susan B

    2014-01-01

    The hydration structure of Ba^{2+} ion is important for understanding blocking mechanisms in potassium ion channels. Here, we combine statistical mechanical theory, ab initio molecular dynamics simulations, and electronic structure methods to calculate the hydration free energy and local hydration structure of Ba^{2+}(aq). The predicted hydration free energy (-302.9$\\pm$0.7 kcal/mol) matches the experimental value (-302.56 kcal/mol) when the fully occupied and exclusive inner solvation shell is treated. In the local environment defined by the inner and first shell of hydrating waters, Ba^{2+} is directly coordinated by eight (8) waters. Octa-coordination resembles the structure of Ba^{2+} and K^+ bound in potassium ion channels, but differs from the local hydration structure of K^+(aq) determined earlier.

  5. Pore capillary pressure and saturation of methane hydrate bearing sediments

    Institute of Scientific and Technical Information of China (English)

    SUN Shicai; LIU Changling; YE Yuguang; LIU Yufeng

    2014-01-01

    To better understand the relationship between the pore capillary pressure and hydrate saturation in sedi-ments, a new method was proposed. First, the phase equilibria of methane hydrate in fine-grained silica sands were measured. As to the equilibrium data, the pore capillary pressure and saturation of methane hydrate were calculated. The results showed that the phase equilibria of methane hydrates in fine-grained silica sands changed due to the depressed activity of pore water caused by the surface group and negatively charged characteristic of silica particles as well as the capillary pressure in small pores together. The capil-lary pressure increased with the increase of methane hydrate saturation due to the decrease of the available pore space. However, the capillary-saturation relationship could not yet be described quantitatively because of the stochastic habit of hydrate growth.

  6. Particle size and hydration medium effects on hydration properties and sugar release of wheat straw fibers

    International Nuclear Information System (INIS)

    Wheat straw is gaining importance as a feedstock for the production of biofuels and high value-added bioproducts. Several pretreatments recover the fermentable fraction involving the use of water or aqueous solutions. Therefore, hydration properties of wheat straw fibers play an important role in improving pretreatment performance. In this study, the water retention capacity (WRC) and swelling of wheat straw fibers were studied using water, propylene glycol (PPG) and an effluent from a H2-producing reactor as the hydration media with three particle sizes (3.35, 2.00 and 0.212 mm). The effects of swelling were analyzed by optical and confocal laser scanning microscopy (CLSM). The highest WRC was reached with the effluent medium (9.84 ± 0.87 g g−1 in 4 h), followed by PPG (8.52 ± 0.18 g g−1 in 1 h) and water (8.74 ± 0.76 g g−1 in 10 h). The effluent hydration treatment had a synergic effect between the enzymes present and the water. The particle size had a significant effect on the WRC (P < 0.01), the highest values were reached with 3.35 mm fibers. The CLSM images showed that finer fibers were subjected to a shaving effect due to the grinding affecting its capacity to absorb the hydration medium. The microscopic analysis showed the increase in the width of the epidermal cells after the hydration and a more undulating cell wall likely due to the hydration of the amorphous regions in the cellulose microfibrils. The sugar release was determined, achieving the highest glucose content with the effluent hydration treatment. - Highlights: • Water retention capacity (WRC) and swelling of wheat straw fibers were studied. • The highest WRC was achieved with a biological effluent. • The enzymatic activity in the biological effluent yielded the highest sugar release. • Finer fibers showed a shaving effect that affected its capacity to absorb water. • A more undulating cell wall was visualized after the hydration

  7. Insights into methane hydrate formation, agglomeration, and dissociation in water + diesel oil dispersed system

    International Nuclear Information System (INIS)

    Highlights: • Hydrate agglomeration occurs at initial hydrate formation or under shutting down stages. • The agglomeration of hydrate is inhibited and dispersed with the action of anti-agglomerants. • The appearance of surface water may cause the agglomeration of hydrate during hydrate dissociation. • A mechanism was proposed to describe hydrate dissociation from water in oil dispersed system. - Abstract: Methane hydrate formation and dissociation in (5 vol% water + 95 vol% diesel oil) dispersed system containing a combined anti-agglomerant were experimentally studied using a high pressure autoclave installed with particle video microscope and focused beam reflectance measurement probes. The agglomeration of hydrate was found to occur at the initial hydrate formation stage. With the continuous formation of hydrate, the agglomeration of hydrate will be inhibited and hydrate was dispersed with the action of the anti-agglomerant. The agglomeration of hydrate also occurs when the hydrate containing fluid is under static state for a certain time. Larger hydrate particles attached by gas bubble with grape-like shape were found during hydrate dissociation. The dissociated surface water would contact with un-dissociated hydrate and accumulate to larger water/hydrate particles may be the reason that causes the agglomeration during initial hydrate dissociation process. A mechanism was proposed to describe hydrate dissociation from water in oil dispersed system

  8. Arguments for a Comprehensive Laboratory Research Subprogram on Hydrocarbon Gas Hydrates and Hydrate-Sediment Aggregates in the 2005-2010 DOE Methane Hydrate R & D Program

    Science.gov (United States)

    Kirby, S. H.

    2005-12-01

    Field observations of natural hydrocarbon clathrate hydrates, including responses to drilling perturbations of hydrates, well logging and analysis of drill core, and field geophysics are, combined with theoretical modeling, justifiably key activities of the authorized 2005-2010 DOE Methane Hydrate Program. It is argued in this presentation that sustained fundamental laboratory research amplifies, extends and verifies results obtained from field and modeling investigations and does so in a cost-effective way. Recent developments of hydrocarbon clathrate hydrate and sediment aggregate synthesis methods, applications of in-situ optical cell, Raman, NMR, x-ray tomography and neutron diffraction techniques, and cryogenic x-ray and SEM methods re-enforce the importance of such lab investigations. Moreover, there are large data gaps for hydrocarbon-hydrate and hydrate-sediment-aggregate properties. We give three examples: 1) All natural hydrocarbon hydrates in sediment core have been altered to varying degrees by their transit, storage, depressurization, and subsequent lab investigations, as are well-log observations during drilling operations. Interpretation of drill core properties and structure and well logs are also typically not unique. Emulations of the pressure-temperature-deformation-time histories of synthetic samples offer a productive way of gaining insight into how natural samples and logging measurements may be compositionally and texturally altered during sampling and handling. 2) Rock physics models indicate that the effects of hydrates on sediment properties depend on the manner in which hydrates articulate with the sediment matrix (their conformation). Most of these models have not been verified by direct testing using hydrocarbon hydrates with conformation checked by optical cell observations or cryogenic SEM. Such tests are needed and technically feasible. 3) Modeling the effects of exchanges of heat, multiphase fluid fluxes, and deformation involve

  9. Hydration behaviour of synthetic saponite at variable relative humidity

    Indian Academy of Sciences (India)

    Karmous Mohamed Salah; Jean Louis Robert

    2011-10-01

    Hydration behaviour of synthetic saponite was examined by X-ray powder diffraction simulation at various relative humidities (RH). The basal spacing of the Ca-saponite increased stepwise with increase in RH. The (00) reflections observed reflect single or dual hydration states of smectite. Quasi-rational, intermediate, or asymmetrical reflections were observed for all XRD patterns and reflecting heterogeneity of the samples, especially along the transition between two hydration states.

  10. Comparative Hydration Behavior of Metakaolin-Microfine System

    OpenAIRE

    Sood, Vivek; Kumar, Ashok; Agarwal, S. K.

    2014-01-01

    In the present study comparative hydration behaviour of cement with metakaolin and-microfine (ultra fine slag) system has been investigated. Various properties like pozzolanic activity, compressive strength, heat of hydration, XRD of control, hydrated and blended metakaolin/microfine-cement compositions has been compared. With 5%, 7.5% and 10% replacement of cement by metakaolin and microfine, pozzolanic activity increases about 22%, 27%,13% for metakaolin and 23%,35%,20% for microfine compar...

  11. Influence of PC superplasticizers on tricalcium silicate hydration.

    OpenAIRE

    Pourchet, S.; Comparet, C.; Nicoleau, L.; Nonat, A.

    2007-01-01

    The influence of polycarboxylate superplasticizers with variations of content of anionic groups was studied on pure tricalcium silicate hydration. The hydration in diluted suspension has been investigated by conductimetry, calorimetry, and ionic and total organic carbon analysis of the liquid phase. The tricalcium silicate hydration is always delayed in presence of polycarboxylate superplasticizer. Moreover, the delay can be correlated with the number of carboxylate groups which are on the ad...

  12. New Methods for Gas Hydrate Energy and Climate Studies

    Science.gov (United States)

    Ruppel, C. D.; Pohlman, J.; Waite, W. F.; Hunt, A. G.; Stern, L. A.; Casso, M.

    2015-12-01

    Over the past few years, the USGS Gas Hydrates Project has focused on advancements designed to enhance both energy resource and climate-hydrate interaction studies. On the energy side, the USGS now manages the Pressure Core Characterization Tools (PCCTs), which includes the Instrumented Pressure Testing Chamber (IPTC) that we have long maintained. These tools, originally built at Georgia Tech, are being used to analyze hydrate-bearing sediments recovered in pressure cores during gas hydrate drilling programs (e.g., Nankai 2012; India 2015). The USGS is now modifying the PCCTs for use on high-hydrate-saturation and sand-rich sediments and hopes to catalyze third-party tool development (e.g., visualization). The IPTC is also being used for experiments on sediments hosting synthetic methane hydrate, and our scanning electron microscope has recently been enhanced with a new cryo-stage for imaging hydrates. To support climate-hydrate interaction studies, the USGS has been re-assessing the amount of methane hydrate in permafrost-associated settings at high northern latitudes and examined the links between methane carbon emissions and gas hydrate dissociation. One approach relies on the noble gas signature of methane emissions. Hydrate dissociation uniquely releases noble gases partitioned by molecular weight, providing a potential fingerprint for hydrate-sourced methane emissions. In addition, we have linked a DOC analyzer with an IRMS at Woods Hole Oceanographic Institution, allowing rapid and precise measurement of DOC and DIC concentrations and carbon isotopic signatures. The USGS has also refined methods to measure real-time sea-air flux of methane and CO2 using cavity ring-down spectroscopy measurements coupled with other data. Acquiring ~8000 km of data on the Western Arctic, US Atlantic, and Svalbard margins, we have tested the Arctic methane catastrophe hypothesis and the link between seafloor methane emissions and sea-air methane flux.

  13. Methane gas hydrate effect on sediment acoustic and strength properties

    Science.gov (United States)

    Winters, W.J.; Waite, W.F.; Mason, D.H.; Gilbert, L.Y.; Pecher, I.A.

    2007-01-01

    To improve our understanding of the interaction of methane gas hydrate with host sediment, we studied: (1) the effects of gas hydrate and ice on acoustic velocity in different sediment types, (2) effect of different hydrate formation mechanisms on measured acoustic properties (3) dependence of shear strength on pore space contents, and (4) pore pressure effects during undrained shear. A wide range in acoustic p-wave velocities (Vp) were measured in coarse-grained sediment for different pore space occupants. Vp ranged from less than 1 km/s for gas-charged sediment to 1.77–1.94 km/s for water-saturated sediment, 2.91–4.00 km/s for sediment with varying degrees of hydrate saturation, and 3.88–4.33 km/s for frozen sediment. Vp measured in fine-grained sediment containing gas hydrate was substantially lower (1.97 km/s). Acoustic models based on measured Vp indicate that hydrate which formed in high gas flux environments can cement coarse-grained sediment, whereas hydrate formed from methane dissolved in the pore fluid may not. The presence of gas hydrate and other solid pore-filling material, such as ice, increased the sediment shear strength. The magnitude of that increase is related to the amount of hydrate in the pore space and cementation characteristics between the hydrate and sediment grains. We have found, that for consolidation stresses associated with the upper several hundred meters of sub-bottom depth, pore pressures decreased during shear in coarse-grained sediment containing gas hydrate, whereas pore pressure in fine-grained sediment typically increased during shear. The presence of free gas in pore spaces damped pore pressure response during shear and reduced the strengthening effect of gas hydrate in sands.

  14. Natural Gas Hydrates - from the Microstructure towards a Geological Understanding

    OpenAIRE

    Klapp, Stephan A.

    2009-01-01

    The dissertation addresses mineralogical characteristics of natural gas hydrates from cold seeps in the Gulf of Mexico and the eastern Black Sea. The investigated properties are the crystal structure, the crystallite sizes and size distributions, the compositions of the hydrate-forming gases, the hydrate porosity as well as the grain boundary networks. That was accomplished using X-ray diffraction, gas chromatography, Raman-spectroscopy, and scanning electron microscopy. "Bragg tomography" wa...

  15. Effects of salinity on methane gas hydrate system

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Using an approximately analytical formation,we extend the steady state model of the pure methane hydrate system to include the salinity based on the dynamic model of the methane hydrate system.The top and bottom boundaries of the methane hydrate stability zone (MHSZ) and the actual methane hydrate zone (MHZ),and the top of free gas occurrence are determined by using numerical methods and the new steady state model developed in this paper.Numerical results show that the MHZ thickness becomes thinner with increasing the salinity,and the stability is lowered and the base of the MHSZ is shifted toward the seafloor in the presence of salts.As a result,the thickness of actual hydrate occurrence becomes thinner compared with that of the pure water case.On the other hand,since lower solubility reduces the amount of gas needed to form methane hydrate,the existence of salts in seawater can actually promote methane gas hydrate formation in the hydrate stability zone.Numerical modeling also demonstrates that for the salt-water case the presence of methane within the field of methane hydrate stability is not sufficient to ensure the occurrence of gas hydrate,which can only form when the methane concentration dissolved in solution with salts exceeds the local methane solubility in salt water and if the methane flux exceeds a critical value corresponding to the rate of diffusive methane transport.In order to maintain gas hydrate or to form methane gas hydrate in marine sediments,a persistent supplied methane probably from biogenic or thermogenic processes,is required to overcome losses due to diffusion and advection.

  16. Preventing Coal and Gas Outburst Using Methane Hydration

    Institute of Scientific and Technical Information of China (English)

    吴强; 何学秋

    2003-01-01

    According to the characteristics of the methane hydrate condensing and accumulating methane, authors put forward a new technique thought way to prevent the accident of coal and gas outburst by urging the methane in the coal seams to form hydrate. The paper analyzes the feasibility of forming the methane hydrate in the coal seam from the several sides, such as, temperature,pressure, and gas components, and the primary trial results indicate the problems should be settled before the industrialization appliance realized.

  17. Geomechanical Performance of Hydrate-Bearing Sediment in Offshore Environments

    Energy Technology Data Exchange (ETDEWEB)

    Stephen Holditch; Tad Patzek; Jonny Rutqvist; George Moridis; Richard Plumb

    2008-03-31

    The objective of this multi-year, multi-institutional research project was to develop the knowledge base and quantitative predictive capability for the description of geomechanical performance of hydrate-bearing sediments (hereafter referred to as HBS) in oceanic environments. The focus was on the determination of the envelope of hydrate stability under conditions typical of those related to the construction and operation of offshore platforms. We have developed a robust numerical simulator of hydrate behavior in geologic media by coupling a reservoir model with a commercial geomechanical code. We also investigated the geomechanical behavior of oceanic HBS using pore-scale models (conceptual and mathematical) of fluid flow, stress analysis, and damage propagation. The objective of the UC Berkeley work was to develop a grain-scale model of hydrate-bearing sediments. Hydrate dissociation alters the strength of HBS. In particular, transformation of hydrate clusters into gas and liquid water weakens the skeleton and, simultaneously, reduces the effective stress by increasing the pore pressure. The large-scale objective of the study is evaluation of geomechanical stability of offshore oil and gas production infrastructure. At Lawrence Berkeley National Laboratory (LBNL), we have developed the numerical model TOUGH + Hydrate + FLAC3D to evaluate how the formation and disassociation of hydrates in seafloor sediments affects seafloor stability. Several technical papers were published using results from this model. LBNL also developed laboratory equipment and methods to produce realistic laboratory samples of sediments containing gas hydrates so that mechanical properties could be measured in the laboratory. These properties are required to run TOUGH + Hydrate + FLAC3D to evaluate seafloor stability issues. At Texas A&M University we performed a detailed literature review to determine what gas hydrate formation properties had been measured and reported in the literature. We

  18. Critical pressure and multiphase flow in Blake Ridge gas hydrates

    Science.gov (United States)

    Flemings, P.B.; Liu, Xiuying; Winters, W.J.

    2003-01-01

    We use core porosity, consolidation experiments, pressure core sampler data, and capillary pressure measurements to predict water pressures that are 70% of the lithostatic stress, and gas pressures that equal the lithostatic stress beneath the methane hydrate layer at Ocean Drilling Program Site 997, Blake Ridge, offshore North Carolina. A 29-m-thick interconnected free-gas column is trapped beneath the low-permeability hydrate layer. We propose that lithostatic gas pressure is dilating fractures and gas is migrating through the methane hydrate layer. Overpressured gas and water within methane hydrate reservoirs limit the amount of free gas trapped and may rapidly export methane to the seafloor.

  19. Micromechanical cohesion force measurements to determine cyclopentane hydrate interfacial properties.

    Science.gov (United States)

    Aman, Zachary M; Joshi, Sanjeev E; Sloan, E Dendy; Sum, Amadeu K; Koh, Carolyn A

    2012-06-15

    Hydrate aggregation and deposition are critical factors in determining where and when hydrates may plug a deepwater flowline. We present the first direct measurement of structure II (cyclopentane) hydrate cohesive forces in the water, liquid hydrocarbon and gas bulk phases. For fully annealed hydrate particles, gas phase cohesive forces were approximately twice that obtained in a liquid hydrocarbon phase, and approximately six times that obtained in the water phase. Direct measurements show that hydrate cohesion force in a water-continuous bulk may be only the product of solid-solid cohesion. When excess water was present on the hydrate surface, gas phase cohesive forces increased by a factor of three, suggesting the importance of the liquid or quasi-liquid layer (QLL) in determining cohesive force. Hydrate-steel adhesion force measurements show that, when the steel surface is coated with hydrophobic wax, forces decrease up to 96%. As the micromechanical force technique is uniquely capable of measuring hydrate-surface forces with variable contact time, the present work contains significant implications for hydrate applications in flow assurance. PMID:22484169

  20. Mechanical properties of sand, silt, and clay containing tetrahydrofuran hydrate

    Science.gov (United States)

    Yun, T.S.; Santamarina, C.J.; Ruppel, C.

    2007-01-01

    The mechanical behavior of hydrate-bearing sediments subjected to large strains has relevance for the stability of the seafloor and submarine slopes, drilling and coring operations, and the analysis of certain small-strain properties of these sediments (for example, seismic velocities). This study reports on the results of comprehensive axial compression triaxial tests conducted at up to 1 MPa confining pressure on sand, crushed silt, precipitated silt, and clay specimens with closely controlled concentrations of synthetic hydrate. The results show that the stress-strain behavior of hydrate-bearing sediments is a complex function of particle size, confining pressure, and hydrate concentration. The mechanical properties of hydrate-bearing sediments at low hydrate concentration (probably 50% of pore space), the behavior becomes more independent of stress because the hydrates control both stiffness and strength and possibly the dilative tendency of sediments by effectively increasing interparticle coordination, cementing particles together, and filling the pore space. The cementation contribution to the shear strength of hydrate-bearing sediments decreases with increasing specific surface of soil minerals. The lower the effective confining stress, the greater the impact of hydrate formation on normalized strength.

  1. Hydrate control for WAG injection in the Ekofisk field

    Energy Technology Data Exchange (ETDEWEB)

    Lekvam, Knut; Surguchev, Leonid M.; Ekrann, Steinar; Svartaas, Thor Martin; Kelland, Malcolm; Nilsson, Svante; Oevsthus, Jorun; Gjoevikli, Nils B.

    1997-12-31

    The report relates to a hydrate formation project for the Ekofisk field on the Norwegian continental shelf. To remove the possible hydrate formation problems during WAG (Water Alternating Gas) treatment, the following project was conducted to estimate roughly the distance from the injection well that hydrate formation can be prevented by whatever treatment is most appropriate. The first aim was to test experimentally whether selected kinetic hydrate inhibitors could be used, and in which concentrations and quantities. In addition evaluations were done to calculate the required volume of the inhibitor solutions that have to be injected to prevent mixing of uninhibited water and gas. 8 figs., 8 tabs.

  2. Formation of hydrate plug within rectangular natural gas passage

    Energy Technology Data Exchange (ETDEWEB)

    Seong, K.; Song, M.H.; Ahn, J.H.; Yoo, K.S. [Dong Guk Univ., Joong-ku, Seoul (Korea, Republic of)

    2008-07-01

    Oil and gas reservoirs in off-shore shallow areas are being depleted. At the same time, the industry is expanding its production sites into deeper waters resulting in higher pressure and lower temperature and more isolated locations. In response, connecting pipelines have been extended, but because of these pressure, temperature and distance changes in pipelines, a more favorable condition for hydrate formation is created, making the problem of flow assurance more critical for safe and economic operations at deep off-shore oil and gas production sites. Another challenge in flow assurance lies in hydrate formation and potential blockage due to hydrate plugs in gas pipelines, where no free water phase is present. This paper presented an experimental study that examined the formation and the growth of hydrates from a gas mixture of methane and propane with different moisture concentrations. The hydrates were formed in a rectangular passage cooled to temperatures below equilibrium hydrate formation temperature. The paper described the experimental procedure and apparatus that was designed and fabricated for the study. A schematic layout of the hydrate formation and plug test experimental apparatus was illustrated. The paper also described the results of two sets of experiments that were conducted. It was concluded that with enough moisture content, hydrates formed without a fresh water phase under equilibrium conditions. It was also concluded that the results of the study could be used in verifying numerical models developed to predict hydrate plugging of natural gas pipelines. 4 refs., 6 figs.

  3. Ethylene Separation via Hydrate Formation in W/O Emulsions

    Directory of Open Access Journals (Sweden)

    Yong Pan

    2015-05-01

    Full Text Available An hybrid absorption-hydration method was adopted to recover C2H4 from C2H4/CH4 binary gas mixtures and the hydrate formation conditions of C2H4/CH4 mixtures was studied experimentally in diesel in water (w/o emulsions. Span 20 at a concentration of 1.0 wt% in the aqueous phase was added to form water in diesel emulsions before hydrate formation and then hydrate in diesel slurry was separated after hydrate formation. The influences of initial gas-liquid volume ratio (53–142, pressure (3.4–5.4 MPa, temperature (274.15–278.15 K, water cuts (10–30 vol%, and the mole fraction of C2H4 in feed gas (13.19–80.44 mol% upon the C2H4 separation efficiency were systematically investigated. The experimental results show that ethylene can be enriched in hydrate slurry phase with high separation factor (S and recovery ratio (R. Most hydrate formation finished in 20 min, after that, the hydrate formation rate became very slow. The conclusion is useful for determining the suitable operation conditions when adopting an absorption-hydration method to separate C2H4/CH4.

  4. Research on Hydration of Steel Slag Cement Activated with Waterglass

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    This paper studied the hydration and strength influence factors of Steel Slag Cement (SSC),such as the quantity of steel slag and slag and the dosage of additive.The results show that:(a) In the process of hydration of SSC,steel slag and slag activate each other;(b) Waterglass's structure forms the preliminary skeleton of SSC,and the hydration products of SSC link or fill in the skeleton;(c) Sodium in waterglass is the catalytic and its concentration does not change in the process of hydration.(d) Structure of activation is a significant factor to the property of SSC.

  5. Kinetics of hydrate formation using gas bubble suspended in water

    Institute of Scientific and Technical Information of China (English)

    马昌峰; 陈光进; 郭天民

    2002-01-01

    An innovative experimental technique, which was devised to study the effects of temperature and pressure on the rate of hydrate formation at the surface of a gas bubble suspended in a stagnant water phase, was adapted in this work. Under such conditions, the hydrate-growth process is free from dynamic mass transfer factors. The rate of hydrate formation of methane and carbon dioxide has been systematically studied. The measured hydrate-growth data were correlated by using the molar Gibbs free energy as driving force. In the course of the experiments, some interesting surface phenomena were observed.

  6. Nuclear Well Log Properties of Natural Gas Hydrate Reservoirs

    Science.gov (United States)

    Burchwell, A.; Cook, A.

    2015-12-01

    Characterizing gas hydrate in a reservoir typically involves a full suite of geophysical well logs. The most common method involves using resistivity measurements to quantify the decrease in electrically conductive water when replaced with gas hydrate. Compressional velocity measurements are also used because the gas hydrate significantly strengthens the moduli of the sediment. At many gas hydrate sites, nuclear well logs, which include the photoelectric effect, formation sigma, carbon/oxygen ratio and neutron porosity, are also collected but often not used. In fact, the nuclear response of a gas hydrate reservoir is not known. In this research we will focus on the nuclear log response in gas hydrate reservoirs at the Mallik Field at the Mackenzie Delta, Northwest Territories, Canada, and the Gas Hydrate Joint Industry Project Leg 2 sites in the northern Gulf of Mexico. Nuclear logs may add increased robustness to the investigation into the properties of gas hydrates and some types of logs may offer an opportunity to distinguish between gas hydrate and permafrost. For example, a true formation sigma log measures the thermal neutron capture cross section of a formation and pore constituents; it is especially sensitive to hydrogen and chlorine in the pore space. Chlorine has a high absorption potential, and is used to determine the amount of saline water within pore spaces. Gas hydrate offers a difference in elemental composition compared to water-saturated intervals. Thus, in permafrost areas, the carbon/oxygen ratio may vary between gas hydrate and permafrost, due to the increase of carbon in gas hydrate accumulations. At the Mallik site, we observe a hydrate-bearing sand (1085-1107 m) above a water-bearing sand (1107-1140 m), which was confirmed through core samples and mud gas analysis. We observe a decrease in the photoelectric absorption of ~0.5 barnes/e-, as well as an increase in the formation sigma readings of ~5 capture units in the water-bearing sand as

  7. Life Origination Hydrate Hypothesis (LOH-Hypothesis

    Directory of Open Access Journals (Sweden)

    Victor Ostrovskii

    2012-01-01

    Full Text Available The paper develops the Life Origination Hydrate Hypothesis (LOH-hypothesis, according to which living-matter simplest elements (LMSEs, which are N-bases, riboses, nucleosides, nucleotides, DNA- and RNA-like molecules, amino-acids, and proto-cells repeatedly originated on the basis of thermodynamically controlled, natural, and inevitable processes governed by universal physical and chemical laws from CH4, niters, and phosphates under the Earth's surface or seabed within the crystal cavities of the honeycomb methane-hydrate structure at low temperatures; the chemical processes passed slowly through all successive chemical steps in the direction that is determined by a gradual decrease in the Gibbs free energy of reacting systems. The hypothesis formulation method is based on the thermodynamic directedness of natural movement and consists ofan attempt to mentally backtrack on the progression of nature and thus reveal principal milestones alongits route. The changes in Gibbs free energy are estimated for different steps of the living-matter origination process; special attention is paid to the processes of proto-cell formation. Just the occurrence of the gas-hydrate periodic honeycomb matrix filled with LMSEs almost completely in its final state accounts for size limitation in the DNA functional groups and the nonrandom location of N-bases in the DNA chains. The slowness of the low-temperature chemical transformations and their “thermodynamic front” guide the gross process of living matter origination and its successive steps. It is shown that the hypothesis is thermodynamically justified and testable and that many observed natural phenomena count in its favor.

  8. Electrical properties of methane hydrate + sediment mixtures: The σ of CH4 Hydrate + Sediment

    Energy Technology Data Exchange (ETDEWEB)

    Du Frane, Wyatt L. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Stern, Laura A. [U. S. Geological Survey, Menlo Park, CA (United States); Constable, Steven [Scripps Institution of Oceanography, La Jolla, CA (United States); Weitemeyer, Karen A. [Scripps Institution of Oceanography, La Jolla, CA (United States); National Oceanography Centre Southampton (United Kingdom), Univ. of Southampton Waterfront Campus, Southampton (United Kingdom); Smith, Megan M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Roberts, Jeffery J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2015-07-30

    Knowledge of the electrical properties of multicomponent systems with gas hydrate, sediments, and pore water is needed to help relate electromagnetic (EM) measurements to specific gas hydrate concentration and distribution patterns in nature. We built a pressure cell capable of measuring in situ electrical properties of multicomponent systems such that the effects of individual components and mixing relations can be assessed. We first established the temperature-dependent electrical conductivity (σ) of pure, single-phase methane hydrate to be ~5 orders of magnitude lower than seawater, a substantial contrast that can help differentiate hydrate deposits from significantly more conductive water-saturated sediments in EM field surveys. We report σ measurements of two-component systems in which methane hydrate is mixed with variable amounts of quartz sand or glass beads. Sand by itself has low σ but is found to increase the overall σ of mixtures with well-connected methane hydrate. Alternatively, the overall σ decreases when sand concentrations are high enough to cause gas hydrate to be poorly connected, indicating that hydrate grains provide the primary conduction path. Our measurements suggest that impurities from sand induce chemical interactions and/or doping effects that result in higher electrical conductivity with lower temperature dependence. Finally, these results can be used in the modeling of massive or two-phase gas-hydrate-bearing systems devoid of conductive pore water. Further experiments that include a free water phase are the necessary next steps toward developing complex models relevant to most natural systems.

  9. Are seafloor pockmarks on the Chatham Rise, New Zealand, linked to CO2 hydrates? Gas hydrate stability considerations.

    Science.gov (United States)

    Pecher, I. A.; Davy, B. W.; Rose, P. S.; Coffin, R. B.

    2015-12-01

    Vast areas of the Chatham Rise east of New Zealand are covered by seafloor pockmarks. Pockmark occurrence appears to be bathymetrically controlled with a band of smaller pockmarks covering areas between 500 and 700 m and large seafloor depressions beneath 800 m water depth. The current depth of the top of methane gas hydrate stability in the ocean is about 500 m and thus, we had proposed that pockmark formation may be linked to methane gas hydrate dissociation during sealevel lowering. However, while seismic profiles show strong indications of fluid flow, geochemical analyses of piston cores do not show any evidence for current or past methane flux. The discovery of Dawsonite, indicative of significant CO2 flux, in a recent petroleum exploration well, together with other circumstantial evidence, has led us to propose that instead of methane hydrate, CO2 hydrate may be linked to pockmark formation. We here present results from CO2 hydrate stability calculations. Assuming water temperature profiles remain unchanged, we predict the upper limit of pockmark occurrence to coincide with the top of CO2 gas hydrate stability during glacial-stage sealevel lowstands. CO2 hydrates may therefore have dissociated during sealevel lowering leading to gas escape and pockmark formation. In contrast to our previous model linking methane hydrate dissociation to pockmark formation, gas hydrates would dissociate beneath a shallow base of CO2 hydrate stability, rather than on the seafloor following upward "grazing" of the top of methane hydrate stability. Intriguingly, at the water depths of the larger seafloor depressions, the base of gas hydrate stability delineates the phase boundary between CO2 hydrates and super-saturated CO2. We caution that because of the high solubility of CO2, dissociation from hydrate to free gas or super-saturated CO2 would imply high concentrations of CO2 and speculate that pockmark formation may be linked to CO2 hydrate dissolution rather than dissociation

  10. Calcium bromide hydration for heat storage systems

    OpenAIRE

    Ai Niwa; Noriyuki Kobayashi

    2015-01-01

    A chemical reaction is a common and simple way to produce heat for a heat storage system. The reaction produces heat energy without the use of electricity or fuel. The goal of this study was to develop a heat storage system for use in automobiles, which is able to provide heat rapidly via a hydration reaction. A heat storage system without an evaporator stores high-density heat and has a high heat output rate since the solid–liquid product that is formed is transferred as a heat medium to the...

  11. [Terminal phase hydration, pain and delirium

    DEFF Research Database (Denmark)

    Heick, A.

    2009-01-01

    Hydration of the terminal patient may relieve confusion and complaints of "dry mouth". But it may worsen oedema of the brain, lungs, and extremities, worsen terminal rattling and cause a need for frequent changing of diapers. The decision of whether and how to treat a dying patient with fluids sh...... should therefore be an integral part of the terminal treatment plan. Such plans should be discussed with the patient and the relatives, and it will very likely need to be revised as the condition worsens Udgivelsesdato: 2009/9/14...

  12. Investigating the Metastability of Clathrate Hydrates for Energy Storage

    Energy Technology Data Exchange (ETDEWEB)

    Koh, Carolyn Ann [Colorado School of Mines

    2014-11-18

    Important breakthrough discoveries have been achieved from the DOE award on the key processes controlling the synthesis and structure-property relations of clathrate hydrates, which are critical to the development of clathrate hydrates as energy storage materials. Key achievements include: (i) the discovery of key clathrate hydrate building blocks (stable and metastable) leading to clathrate hydrate nucleation and growth; (ii) development of a rapid clathrate hydrate synthesis route via a seeding mechanism; (iii) synthesis-structure relations of H2 + CH4/CO2 binary hydrates to control thermodynamic requirements for energy storage and sequestration applications; (iv) discovery of a new metastable phase present during clathrate hydrate structural transitions. The success of our research to-date is demonstrated by the significant papers we have published in high impact journals, including Science, Angewandte Chemie, J. Am. Chem. Soc. Intellectual Merits of Project Accomplishments: The intellectual merits of the project accomplishments are significant and transformative, in which the fundamental coupled computational and experimental program has provided new and critical understanding on the key processes controlling the nucleation, growth, and thermodynamics of clathrate hydrates containing hydrogen, methane, carbon dioxide, and other guest molecules for energy storage. Key examples of the intellectual merits of the accomplishments include: the first discovery of the nucleation pathways and dominant stable and metastable structures leading to clathrate hydrate formation; the discovery and experimental confirmation of new metastable clathrate hydrate structures; the development of new synthesis methods for controlling clathrate hydrate formation and enclathration of molecular hydrogen. Broader Impacts of Project Accomplishments: The molecular investigations performed in this project on the synthesis (nucleation & growth)-structure-stability relations of clathrate

  13. Physicochemical and structural studies of clathrate hydrates of tetrabutylammonium polyacrylates.

    Science.gov (United States)

    Terekhova, Irina S; Manakov, Andrey Yu; Komarov, Vladislav Yu; Villevald, Galina V; Burdin, Alexander A; Karpova, Tamara D; Aladko, Eugeny Ya

    2013-03-01

    In this work, physicochemical and structural studies have been carried out for semiclathrate hydrates of linear (un-cross-linked) and cross-linked tetrabutylammonium polyacrylates with different degrees of cross-linking of the polymeric guest molecules (n = 0.5, 1, 2, 3%) and different degrees of substitution of proton ions of carboxylic groups in poly(acrylic acid) for TBA cations (x = 1, 0.8, 0.6). The changes in the hydrates' stability and composition depending on the outlined parameters were examined in the course of phase diagram studies of the binary systems water-tetrabutylammonium polyacrylates using differential thermal analysis method and calorimetric measurements of fusion enthalpies of the hydrates. Phase diagram studies of the binary system water-linear tetrabutylammonium polyacrylate revealed the formation of four hydrates. Based on the data of chemical analysis of hydrate crystals the compositions of all hydrates have been determined. Single-crystal X-ray diffraction studies revealed a tetragonal structure, space group 4/m, and unit cell parameters are close for different hydrates and lie in the ranges a = 23.4289-23.4713 Å and c = 12.3280-12.3651 Å (150 K). The structure can be related to tetragonal structure I typical for the clathrate hydrates of tetraalkylammonium salts with monomeric anions. Powder X-ray diffraction analyses confirmed the identity of the above crystal structure to that of the hydrates with cross-linked tetrabutylammonium polyacrylates. The behavior of TBA polyacrylate hydrates under the pressure of methane was studied and quantitative assessment of the gas content in the hydrates was made using volumetric analysis method. PMID:23383955

  14. Gas Hydrate Dissociation in the Ocean

    Science.gov (United States)

    Conroy, Devin; Smith, Stefan Llewellyn

    2006-11-01

    Methane gas is known to exist in extremely large quantities below the sea floor in the sediment of the deep and cold oceanic and in permafrost regions. Due to the large hydrostatic pressure and cool temperatures the gas reacts with the surrounding water to form a crystalline substance known as a gas hydrate. The fate of these reserves is very important to climate on earth because methane is a much more efficient greenhouse gas then carbon dioxide. The dissociation process in general can occur by either a decrease in pressure or an increase in temperature. In this study we concentrate on the latter. Once the hydrate dissociates, water and free gas remain above the phase boundary, occupying a larger volume than the original solid, and are be transported through the sediment. We have modeled this physical mechanism using volume averaged equations in a porous medium with a coupled two-phase flow. The movement of the phase boundary, which is proportional to the rate of heat transfer to this interface, is modeled as a Stefan type melting problem. The resultant governing equations are solved numerically, using a front fixing method to fix the phase boundary, to determine the rate of gas flux through the sediment and the dissociation rate.

  15. Reaction of disodium cromoglycate with hydrated electrons

    International Nuclear Information System (INIS)

    A possible mechanism by which disodium cromoglycate (DSCG) prevents a decrease in regional cerebral blood flow but not hypotension in primates following whole body gamma-irradiation was studied. Several studies have implicated superoxide radicals (O2-.) in intestinal and cerebral vascular disorders following ischemia and ionizing radiation, respectively. O2-. is formed during radiolysis in the reaction between hydrated electrons (e-aq) and dissolved oxygen. For this reason, the efficiency of DSCG to scavenge e-q and possibly prevent the formation of O2-. was studied. Hydrated electrons were produced by photolysis of potassium ferrocyanide solutions. The rate constant, k = 2.92 x 10(10) M-1s-1 for the reaction between e-aq and DSCG was determined in competition experiments using the spin trap 5,5-dimethyl-1-pyrroline-N-oxide (DMPO). This spin trap reacts rapidly with e-aq followed by protonation to yield the ESR observable DMPO-H spin adduct. The results show that DSCG is an efficient e-aq scavenger and may effectively compete with oxygen for e-aq preventing the radiolytic formation of O2-

  16. Reaction of disodium cromoglycate with hydrated electrons

    Energy Technology Data Exchange (ETDEWEB)

    Carmichael, A.J.; Arroyo, C.M.; Cockerham, L.G.

    1988-01-01

    A possible mechanism by which disodium cromoglycate (DSCG) prevents a decrease in regional cerebral blood flow but not hypotension in primates following whole body gamma-irradiation was studied. Several studies have implicated superoxide radicals (O/sub 2//sup -/.) in intestinal and cerebral vascular disorders following ischemia and ionizing radiation, respectively. O/sub 2//sup -/. is formed during radiolysis in the reaction between hydrated electrons (e-aq) and dissolved oxygen. For this reason, the efficiency of DSCG to scavenge e-q and possibly prevent the formation of O/sub 2//sup -/. was studied. Hydrated electrons were produced by photolysis of potassium ferrocyanide solutions. The rate constant, k = 2.92 x 10(10) M-1s-1 for the reaction between e-aq and DSCG was determined in competition experiments using the spin trap 5,5-dimethyl-1-pyrroline-N-oxide (DMPO). This spin trap reacts rapidly with e-aq followed by protonation to yield the ESR observable DMPO-H spin adduct. The results show that DSCG is an efficient e-aq scavenger and may effectively compete with oxygen for e-aq preventing the radiolytic formation of O/sub 2//sup -/..

  17. Calcium bromide hydration for heat storage systems

    Directory of Open Access Journals (Sweden)

    Ai Niwa

    2015-12-01

    Full Text Available A chemical reaction is a common and simple way to produce heat for a heat storage system. The reaction produces heat energy without the use of electricity or fuel. The goal of this study was to develop a heat storage system for use in automobiles, which is able to provide heat rapidly via a hydration reaction. A heat storage system without an evaporator stores high-density heat and has a high heat output rate since the solid–liquid product that is formed is transferred as a heat medium to the object that requires heat. The exothermic heat produced from the solid–liquid reaction was measured, and the relationship between the equivalence ratio and the reaction heat was evaluated. The heat output and heat recovered by the heat storage system, which comprised a reaction vessel and a heat exchanger, were measured. We selected solid CaBr2 because it was the best metal halide for a hydration reaction and had a high heat yield from the dissolution reaction. With this system, we were able to achieve a heat recovery rate of 582 kJ/L-H2O. We found no degradation in the chemical composition of CaBr2 after it being recycled 100 times.

  18. A unified approach for description of gas hydrate formation kinetics in the presence of kinetic promoters in gas hydrate converters

    International Nuclear Information System (INIS)

    Highlights: • A unified kinetic model for description of promoted and non-promoted gas hydrate formation processes is presented. • Effects of impeller speed, promoter concentration and different kinetic promoters are investigated. • A unique region of gas hydrate formation is identified regarding gas hydrate formation processes. • The proposed model is useful for understanding the behavior of gas hydrate formation processes and design of GTH converters. - Abstract: The kinetic promoters have found wide applications in enhancing the rate of energy conversion and storage via gas hydrate formation processes. Effects of different kinetic promoters such as anionic surfactants sodium dodecyl sulfate (SDS), dodecylbenzene sulfonic acid (DBSA), and sodium dodecyl benzene sulfonate (SDBS); cationic surfactants, Cetyl trimethyl ammonium bromide (CTAB), dodecyl trimethyl ammonium bromide (DTAB) and non-ionic surfactants, alkylpolyglucoside (APG), dodecyl polysaccharide glycoside (DPG), TritonX-100 (TX100) on methane (CH4), ethane (C2H6) and propane (C3H8) gas hydrate formation processes are investigated in this work. A macroscopic kinetic model based on the time variations of reaction chemical potential is also presented for global description of gas hydrate formation processes. Experimental gas hydrate formation data are employed to validate the proposed kinetic model. Effects of promoter’s concentrations and agitation intensities on the gas consumption profiles are also investigated. A universal correlation and a unified kinetic map have been proposed for macroscopic description of gas hydrate formation kinetics in the presence or absence of kinetic promoters. According to the presented unified kinetic map, a unique region of gas hydrate formation is identified for the first time. For negligible amounts of kinetic promoters, the presented region disappears and approaches to a unique path at high agitation intensities. The presented unified approach is very useful

  19. INFLUENCE OF CHEMICAL ADDITIVES ON GAS HYDRATE FORMATION

    Institute of Scientific and Technical Information of China (English)

    TANG Cuiping; FAN Shuanshi

    2003-01-01

    One surfactant as sodium dodecyl sulfate (SDS) and one synthesized sample as gas hydrate inhibitor are introduced in this paper. Through experiments we prove sodium dodecyl sulfate can accelerate the formation rate of gas hydrate and the synthesized sample can inhibit the formation and growth.

  20. Lactate Dehydrogenase Catalysis: Roles of Keto, Hydrated, and Enol Pyruvate

    Science.gov (United States)

    Meany, J. E.

    2007-01-01

    Many carbonyl substrates of oxidoreductase enzymes undergo hydration and enolization so that these substrate systems are partitioned between keto, hydrated (gem-diol), and enol forms in aqueous solution. Some oxidoreductase enzymes are subject to inhibition by high concentrations of substrate. For such enzymes, two questions arise pertaining to…

  1. Determination of the Formula of a Hydrate: A Greener Alternative

    Science.gov (United States)

    Klingshirn, Marc A.; Wyatt, Allison F.; Hanson, Robert M.; Spessard, Gary O.

    2008-01-01

    We are currently in the process of incorporating green chemistry throughout the chemistry curriculum. In this article we describe how we applied the principles of green chemistry in one of our first-semester general chemistry courses, specifically in relation to the determination of the formula of a hydrate. We utilize a copper hydrate salt that…

  2. Potential natural gas hydrates resources in Indian Offshore areas

    Digital Repository Service at National Institute of Oceanography (India)

    Sethi, A.K.; Sathe, A.V.; Ramana, M.V.

    (geophysical proxies of gas hydrates). A qualitative map prepared based on the inferred BSRs brought out a deepwater area of about 80,000 sq.km unto 3000 m isobath as favourable for gas hydrate occurrence. Methodology for reprocessing of seismic data...

  3. Salinity-buffered methane hydrate formation and dissociation in gas-rich systems

    Science.gov (United States)

    You, Kehua; Kneafsey, Timothy J.; Flemings, Peter B.; Polito, Peter; Bryant, Steven L.

    2015-02-01

    Methane hydrate formation and dissociation are buffered by salinity in a closed system. During hydrate formation, salt excluded from hydrate increases salinity, drives the system to three-phase (gas, water, and hydrate phases) equilibrium, and limits further hydrate formation and dissociation. We developed a zero-dimensional local thermodynamic equilibrium-based model to explain this concept. We demonstrated this concept by forming and melting methane hydrate from a partially brine-saturated sand sample in a controlled laboratory experiment by holding pressure constant (6.94 MPa) and changing temperature stepwise. The modeled methane gas consumptions and hydrate saturations agreed well with the experimental measurements after hydrate nucleation. Hydrate dissociation occurred synchronously with temperature increase. The exception to this behavior is that substantial subcooling (6.4°C in this study) was observed for hydrate nucleation. X-ray computed tomography scanning images showed that core-scale hydrate distribution was heterogeneous. This implied core-scale water and salt transport induced by hydrate formation. Bulk resistivity increased sharply with initial hydrate formation and then decreased as the hydrate ripened. This study reproduced the salinity-buffered hydrate behavior interpreted for natural gas-rich hydrate systems by allowing methane gas to freely enter/leave the sample in response to volume changes associated with hydrate formation and dissociation. It provides insights into observations made at the core scale and log scale of salinity elevation to three-phase equilibrium in natural hydrate systems.

  4. Thermal Stability and Proton Conductivity of Rare Earth Orthophosphate Hydrates

    DEFF Research Database (Denmark)

    Anfimova, Tatiana; Li, Qingfeng; Jensen, Jens Oluf;

    2014-01-01

    as the rhabdophane structure is preserved. The bound hydrate water is accommodated in the rhabdophane structure and is stable at temperatures of up to 650 oC. The thermal stability of the hydrate water and the phosphate structure are of significance for the proton conductivity. The LaPO4·0.6H2O and NdPO4•0.5H2O......Hydrated orthophosphate powders of three rare earth metals, lanthanum, neodymium and gadolinium, were prepared and studied as potential proton conducting materials for intermediate temperature electrochemical applications. The phosphates undergo a transformation from the rhabdophane structure...... to the monazite structure upon dehydration. The thermal stability of the hydrate is studied and found to contain water of two types, physically adsorbed and structurally bound hydrate water. The adsorbed water is correlated to the specific surface area and can be reversibly recovered when dehydrated as long...

  5. Calorimetric Determination of Enthalpy of Formation of Natural Gas Hydrates

    Institute of Scientific and Technical Information of China (English)

    高军; KennethN.Marsh

    2003-01-01

    This paper reports the measurements of enthalpies of natural gas hydrates in typical natural gas mixture containing methane, ethane, propane and iso-butane at pressure in the vicinity of 2000 kPa (300 psi) and 6900 kPa(1000psi). The measurements were made in a multi-cell differential scanning calorimeter using modified high pressure cells. The enthalpy of water and the enthalpy of dissociation of the gas hydrate were determined from the calorimeter response during slow temperature scanning at constant pressure. The amount of gas released from the dissociation of hydrate was determined from the pumped volume of the high pressure pump. The occupation ratio (mole ratio) of the water to gas and the enthalpy of hydrate formation are subject to uncertainty of 1.5%.The results show that the enthalpy of hydrate formation and the occupation ratio are essentially independent of pressure.

  6. Volatile inventories in clathrate hydrates formed in the primordial nebula

    CERN Document Server

    Mousis, O; Picaud, S; Cordier, D

    2010-01-01

    Examination of ambient thermodynamic conditions suggest that clathrate hydrates could exist in the martian permafrost, on the surface and in the interior of Titan, as well as in other icy satellites. Clathrate hydrates probably formed in a significant fraction of planetesimals in the solar system. Thus, these crystalline solids may have been accreted in comets, in the forming giant planets and in their surrounding satellite systems. In this work, we use a statistical thermodynamic model to investigate the composition of clathrate hydrates that may have formed in the primordial nebula. In our approach, we consider the formation sequence of the different ices occurring during the cooling of the nebula, a reasonable idealization of the process by which volatiles are trapped in planetesimals. We then determine the fractional occupancies of guests in each clathrate hydrate formed at given temperature. The major ingredient of our model is the description of the guest-clathrate hydrate interaction by a spherically a...

  7. Hydration of Portland cement with additions of calcium sulfoaluminates

    Energy Technology Data Exchange (ETDEWEB)

    Le Saout, Gwenn, E-mail: gwenn.le-saout@mines-ales.fr [Empa, Swiss Federal Laboratories for Materials Science and Technology, Concrete and Construction Chemistry Laboratory, Ueberlandstrasse 129, CH-8600 Duebendorf (Switzerland); Lothenbach, Barbara [Empa, Swiss Federal Laboratories for Materials Science and Technology, Concrete and Construction Chemistry Laboratory, Ueberlandstrasse 129, CH-8600 Duebendorf (Switzerland); Hori, Akihiro [DENKA Chemicals GmbH, Wehrhahn-Center, Cantadorstr. 3, D-40211 Duesseldorf (Germany); Higuchi, Takayuki [Denki Kagaku Kogyo Kabushiki Kaisha (DENKA), Omi, Itoigawa, Niigata, 949-0393 (Japan); Winnefeld, Frank [Empa, Swiss Federal Laboratories for Materials Science and Technology, Concrete and Construction Chemistry Laboratory, Ueberlandstrasse 129, CH-8600 Duebendorf (Switzerland)

    2013-01-15

    The effect of mineral additions based on calcium aluminates on the hydration mechanism of ordinary Portland cement (OPC) was investigated using isothermal calorimetry, thermal analysis, X-ray diffraction, scanning electron microscopy, solid state nuclear magnetic resonance and pore solution analysis. Results show that the addition of a calcium sulfoaluminate cement (CSA) to the OPC does not affect the hydration mechanism of alite but controls the aluminate dissolution. In the second blend investigated, a rapid setting cement, the amorphous calcium aluminate reacts very fast to ettringite. The release of aluminum ions strongly retards the hydration of alite but the C-S-H has a similar composition as in OPC with no additional Al to Si substitution. As in CSA-OPC, the aluminate hydration is controlled by the availability of sulfates. The coupling of thermodynamic modeling with the kinetic equations predicts the amount of hydrates and pore solution compositions as a function of time and validates the model in these systems.

  8. Hydration of Portland cement with additions of calcium sulfoaluminates

    International Nuclear Information System (INIS)

    The effect of mineral additions based on calcium aluminates on the hydration mechanism of ordinary Portland cement (OPC) was investigated using isothermal calorimetry, thermal analysis, X-ray diffraction, scanning electron microscopy, solid state nuclear magnetic resonance and pore solution analysis. Results show that the addition of a calcium sulfoaluminate cement (CSA) to the OPC does not affect the hydration mechanism of alite but controls the aluminate dissolution. In the second blend investigated, a rapid setting cement, the amorphous calcium aluminate reacts very fast to ettringite. The release of aluminum ions strongly retards the hydration of alite but the C–S–H has a similar composition as in OPC with no additional Al to Si substitution. As in CSA–OPC, the aluminate hydration is controlled by the availability of sulfates. The coupling of thermodynamic modeling with the kinetic equations predicts the amount of hydrates and pore solution compositions as a function of time and validates the model in these systems.

  9. Methane hydrate formation and dissociation in synthetic seawater

    Institute of Scientific and Technical Information of China (English)

    Vikash Kumar Saw; Iqbal Ahmad; Ajay Mandal; G.Udayabhanu; Sukumar Laik

    2012-01-01

    The formation and dissociation of methane gas hydrate at an interface between synthetic seawater (SSW) and methane gas have been experimentally investigated in the present work.The amount of gas consumed during hydrate formation has been calculated using the real gas equation.Induction time for the formation of hydrate is found to depend on the degree of subcooling.All the experiments were conducted in quiescent system with initial cell pressure of 11.14 MPa.Salinity effects on the onset pressure and temperature of hydrate formation are also observed.The dissociation enthalpies of methane hydrate in synthetic seawater were determined by Clausius-Clapeyron equation based on the measured phase equilibrium data.The dissociation data have been analyzed by existing models and compared with the reported data.

  10. Theoretical description of biomolecular hydration - Application to A-DNA

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, A.E.; Hummer, G. [Los Alamos National Laboratory, NM (United States); Soumpasis, D.M. [Max Planck Inst. for Biophysical Chemistry, Goettingen (Germany)

    1994-12-31

    The local density of water molecules around a biomolecule is constructed from calculated two- and three-points correlation functions of polar solvents in water using a Potential-of-Mean-Force (PMF) expansion. As a simple approximation, the hydration of all polar (including charged) groups in a biomolecule is represented by the hydration of water oxygen in bulk water, and the effect of non-polar groups on hydration are neglected, except for excluded volume effects. Pair and triplet correlation functions are calculated by molecular dynamics simulations. We present calculations of the structural hydration for ideal A-DNA molecules with sequences [d(CG){sub 5}]{sub 2} and [d(C{sub 5}G{sub 5})]{sub 2}. We find that this method can accurately reproduce the hydration patterns of A-DNA observed in neutron diffraction experiments on oriented DNA fibers.

  11. Heat of Hydration of Low Activity Cementitious Waste Forms

    Energy Technology Data Exchange (ETDEWEB)

    Nasol, D. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2015-07-23

    During the curing of secondary waste grout, the hydraulic materials in the dry mix react exothermally with the water in the secondary low-activity waste (LAW). The heat released, called the heat of hydration, can be measured using a TAM Air Isothermal Calorimeter. By holding temperature constant in the instrument, the heat of hydration during the curing process can be determined. This will provide information that can be used in the design of a waste solidification facility. At the Savannah River National Laboratory (SRNL), the heat of hydration and other physical properties are being collected on grout prepared using three simulants of liquid secondary waste generated at the Hanford Site. From this study it was found that both the simulant and dry mix each had an effect on the heat of hydration. It was also concluded that the higher the cement content in the dry materials mix, the greater the heat of hydration during the curing of grout.

  12. The Pore Structure and Hydration Performance of Sulphoaluminate MDF Cement

    Institute of Scientific and Technical Information of China (English)

    HUANG Cong-yun; YUAN Run-zhang; LONG Shi-zong

    2004-01-01

    The hydration and pore structure of sulphoaluminate MDF cement were studied by X-ray diffractometer ( XRD ), scanning electron microscope (SEM) and mercury intrusion porosimeter ( MIP ) etc. The ex-perimental results indicate that hydration products of the materials are entringites ( Aft ), aluminium hydroxide andCSH (Ⅰ) gel etc. Due to its very low water-cement ratio, hydration function is only confined to the surfaces of ce-ment grains, and there is a lot of sulphoaluminate cement in the hardenite which is unhydrated yet. Hydration re-action was rapidly carried under the condition of the heat-pressing. Therefore cement hydrates Aft, CSH (Ⅰ) andaluminium hydroxide gel fill in pores. The expansibility of Aft makes the porosity of MDF cement lower ( less than1 percent ) and the size of pore smaller (80 percent pore was less than 250A), and enhances its strength.

  13. Seismic-Scale Rock Physics of Methane Hydrate

    Energy Technology Data Exchange (ETDEWEB)

    Amos Nur

    2009-01-08

    We quantify natural methane hydrate reservoirs by generating synthetic seismic traces and comparing them to real seismic data: if the synthetic matches the observed data, then the reservoir properties and conditions used in synthetic modeling might be the same as the actual, in-situ reservoir conditions. This approach is model-based: it uses rock physics equations that link the porosity and mineralogy of the host sediment, pressure, and hydrate saturation, and the resulting elastic-wave velocity and density. One result of such seismic forward modeling is a catalogue of seismic reflections of methane hydrate which can serve as a field guide to hydrate identification from real seismic data. We verify this approach using field data from known hydrate deposits.

  14. The role of natural gas hydrates in global changes

    International Nuclear Information System (INIS)

    The main features of gas hydrates which produce global changes are: structure and composition of hydrates, heat of the phase transition and of accumulation and decomposition (about 420 kJ kg-1), the change of the water specific volume (26-32%) under its transition to the hydrate state, and the electric impulse formation between the two phases during the phase transitions of systems. One volume of water contains 70-200 volumes of gas in hydrate state. Gas pressure in the crystal lattice of hydrate is hundreds, even thousands MPa. The hydrate formation zone is associated with frigid areas of Earth sedimentary rocks; on the land, near the polar regions, in the sea, at any latitude at depths >200-500 m. Methane hydrate resources make up about 104 Gt, 99% of them under the sea. The explored resources are 500 Gt. Hydrate methane is, undoubtedly, the energy potential of mankind for the next century, but the rates of the free methane outflow into the atmosphere and their influence on the global climate, ecology, geography, etc. need to be taken into account. The current amount of methane in the atmosphere is about 4.8 Gt. Thus, the average Earth surface temperature is increased by 1.3 K. The annual increase of methane in the atmosphere is 1%. Natural gas hydrates, their spreading and features may cause blowouts of free methane to the atmosphere, much greater than the current biochemical and technogenic sources. Methane may flow from the top and from the bottom of the layer as well under changing thermodynamic conditions, such as decreasing pressure, increase of the geothermal gradient, neotectonic shifts, changing of the hydrate deposits, electric potential. The free methane provides for an increase of CO2, H2O, O3 concentration. The heating effect of methane can be equal to or exceed that of CO2

  15. Reflective terahertz (THz) imaging: system calibration using hydration phantoms

    Science.gov (United States)

    Bajwa, Neha; Garritano, James; Lee, Yoon Kyung; Tewari, Priyamvada; Sung, Shijun; Maccabi, Ashkan; Nowroozi, Bryan; Babakhanian, Meghedi; Sanghvi, Sajan; Singh, Rahul; Grundfest, Warren; Taylor, Zachary

    2013-02-01

    Terahertz (THz) hydration sensing continues to gain traction in the medical imaging community due to its unparalleled sensitivity to tissue water content. Rapid and accurate detection of fluid shifts following induction of thermal skin burns as well as remote corneal hydration sensing have been previously demonstrated in vivo using reflective, pulsed THz imaging. The hydration contrast sensing capabilities of this technology were recently confirmed in a parallel 7 Tesla Magnetic Resonance (MR) imaging study, in which burn areas are associated with increases in local mobile water content. Successful clinical translation of THz sensing, however, still requires quantitative assessments of system performance measurements, specifically hydration concentration sensitivity, with tissue substitutes. This research aims to calibrate the sensitivity of a novel, reflective THz system to tissue water content through the use of hydration phantoms for quantitative comparisons of THz hydration imagery.Gelatin phantoms were identified as an appropriate tissue-mimicking model for reflective THz applications, and gel composition, comprising mixtures of water and protein, was varied between 83% to 95% hydration, a physiologically relevant range. A comparison of four series of gelatin phantom studies demonstrated a positive linear relationship between THz reflectivity and water concentration, with statistically significant hydration sensitivities (p < .01) ranging between 0.0209 - 0.038% (reflectivity: %hydration). The THz-phantom interaction is simulated with a three-layer model using the Transfer Matrix Method with agreement in hydration trends. Having demonstrated the ability to accurately and noninvasively measure water content in tissue equivalent targets with high sensitivity, reflective THz imaging is explored as a potential tool for early detection and intervention of corneal pathologies.

  16. Kinetics Characteristics of Nitrogen Hydrates Respond to Differential Scanning Calorimetry

    Science.gov (United States)

    Chen, Q.; Liu, C.; Ye, Y.; Gong, J.

    2012-12-01

    In this study, a high pressure differential scanning calorimetry (HP DSC) based on thermo-analytical technique was applied to investigate the kinetics and thermodynamics characteristics of nitrogen hydrates. Nitrogen hydrates was synthesized in the sample vessel under different pressures as temperature decreased from 293 to 233 K with a constant cooling rate of 0.2 K/min controlled by the DSC. To measure the hydrates dissociation enthalpies , the temperature was slowly raised up from 233 to 293 K at a constant rate ranging of 0.05 K/min. 1. Peak area on the heat flow curves represents the amount of heat during phase transition. In these experiments, the total water added to the sample vessel (mt) is already known. By integrating the peak areas of ice and hydrate, we know the total heats of ice (Qi) and hydrate (Qh), respectively. As the heat of ice per gram can be measured easily (336.366 J/g), the mass of ice (mi) can be obtain. Then, the dissociation heat of nitrogen hydrate per gram (Hh ) can be calculated by the equation: H(J/g)=Qh/(mt-mi) It is shown that the dissociation heats of nitrogen hydrates are a little larger than ice, but do not change a lot with different pressures. The average value of dissociation heat is 369.158 J/g. 2. During the DSC cooling stage, hydrate formed at temperature much lower than equilibrium. The biggest sub-cooling is about 291 K, while the smallest one is about 279 K. However, during these experiments, the pressure did not show obvious relationship with sub-cooling. It confirmed that even the proper conditions were achieved, formation was still a stochastic process. For one thing, due to the random distribution of dissolved gas in water, the interfacial tension and the water activity were not equal in the whole system. And if there was a free gas phase, which leads to different fugacity on water-gas interface, the stochastic behavior would be more significant in the sample vessel. 3. The energy released from hydrates formation as

  17. Dissolution rates of pure methane hydrate and carbon-dioxide hydrate in undersaturated seawater at 1000-m depth

    Science.gov (United States)

    Rehder, G.; Kirby, S.H.; Durham, W.B.; Stern, L.A.; Peltzer, E.T.; Pinkston, J.; Brewer, P.G.

    2004-01-01

    To help constrain models involving the chemical stability and lifetime of gas clathrate hydrates exposed at the seafloor, dissolution rates of pure methane and carbon-dioxide hydrates were measured directly on the seafloor within the nominal pressure-temperature (P/T) range of the gas hydrate stability zone. Other natural boundary conditions included variable flow velocity and undersaturation of seawater with respect to the hydrate-forming species. Four cylindrical test specimens of pure, polycrystalline CH4 and CO2 hydrate were grown and fully compacted in the laboratory, then transferred by pressure vessel to the seafloor (1028 m depth), exposed to the deep ocean environment, and monitored for 27 hours using time-lapse and HDTV cameras. Video analysis showed diameter reductions at rates between 0.94 and 1.20 ??m/s and between 9.0 and 10.6 ?? 10-2 ??m/s for the CO2 and CH4 hydrates, respectively, corresponding to dissolution rates of 4.15 ?? 0.5 mmol CO2/m2s and 0.37 ?? 0.03 mmol CH4/m2s. The ratio of the dissolution rates fits a diffusive boundary layer model that incorporates relative gas solubilities appropriate to the field site, which implies that the kinetics of the dissolution of both hydrates is diffusion-controlled. The observed dissolution of several mm (CH4) or tens of mm (CO2) of hydrate from the sample surfaces per day has major implications for estimating the longevity of natural gas hydrate outcrops as well as for the possible roles of CO2 hydrates in marine carbon sequestration strategies. ?? 2003 Elsevier Ltd.

  18. Macroscopic investigation of hydrate film growth at the hydrocarbon/water interface

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, C.J.; Miller, K.T.; Koh, C.A.; Sloan, E.D. [Colorado School of Mines, Golden, CO (United States). Dept. of Chemical Engineering

    2008-07-01

    Clathrate hydrates are ice-like crystalline compounds that form as thin porous crystalline films at the interface between the water phase and the hydrocarbon guest molecule phase. The growth characteristics of these hydrate films are important in seafloor carbon dioxide sequestration, gas hydrate transport, and flow assurance in oil and gas pipelines. This paper presented a study that employed digital video microscopy to investigate the hydrate film thickness as a function of time, as well as the propagation rate for methane and cyclopentane hydrate. The purpose of the study was to enhance past measurements of hydrate film growth by incorporating gas consumption measurements simultaneously with film thickness measurements to determine which phase supplied the hydrate former during hydrate formation. The study also advanced the physical knowledge of hydrate formation by relating film formation with the water droplet to hydrate shell conversion. The paper included a schematic of the hydrate film growth apparatus and image acquisition and analysis as well as an illustration of the nucleation of a water droplet immersed in cyclopentane. The results were presented for cyclopentane hydrate film growth; methane hydrate film growth; film growth in an oil/methane/ water system; film growth/development into water phase; and gas consumption for hydrate film growth. The paper also discussed the source of methane for hydrate formation; solubility of methane in water; growth rates; proposed mechanism of hydrate film growth at the hydrocarbon/water interface; and, transferability between hydrate formation for a pool of liquid versus a water droplet. It was concluded that gas consumption data during hydrate formation presented evidence of an aqueous phase supply of hydrate former to the initial hydrate growth, followed by a vapor phase supply of hydrate former in the thickening stage of hydrate film formation. 25 refs., 18 figs.,.

  19. Hydration Structure of the Quaternary Ammonium Cations

    KAUST Repository

    Babiaczyk, Wojtek Iwo

    2010-11-25

    Two indicators of the hydropathicity of small solutes are introduced and tested by molecular dynamics simulations. These indicators are defined as probabilities of the orientation of water molecules\\' dipoles and hydrogen bond vectors, conditional on a generalized distance from the solute suitable for arbitrarily shaped molecules. Using conditional probabilities, it is possible to distinguish features of the distributions in close proximity of the solute. These regions contain the most significant information on the hydration structure but cannot be adequately represented by using, as is usually done, joint distance-angle probability densities. Our calculations show that using our indicators a relative hydropathicity scale for the interesting test set of the quaternary ammonium cations can be roughly determined. © 2010 American Chemical Society.

  20. DNA under Force: Mechanics, Electrostatics, and Hydration

    Directory of Open Access Journals (Sweden)

    Jingqiang Li

    2015-02-01

    Full Text Available Quantifying the basic intra- and inter-molecular forces of DNA has helped us to better understand and further predict the behavior of DNA. Single molecule technique elucidates the mechanics of DNA under applied external forces, sometimes under extreme forces. On the other hand, ensemble studies of DNA molecular force allow us to extend our understanding of DNA molecules under other forces such as electrostatic and hydration forces. Using a variety of techniques, we can have a comprehensive understanding of DNA molecular forces, which is crucial in unraveling the complex DNA functions in living cells as well as in designing a system that utilizes the unique properties of DNA in nanotechnology.

  1. Propane Clathrate Hydrate Formation Accelerated by Methanol.

    Science.gov (United States)

    Amtawong, Jaruwan; Guo, Jin; Hale, Jared S; Sengupta, Suvrajit; Fleischer, Everly B; Martin, Rachel W; Janda, Kenneth C

    2016-07-01

    The role of methanol as both an inhibitor and a catalyst for the formation of clathrate hydrates (CHs) has been a topic of intense study. We report a new quantitative study of the kinetics of propane CH formation at 253 K from the reaction of propane gas with ice particles that have been doped with varying amounts of methanol. We find that methanol significantly accelerates the formation reaction with quite small doping quantities. Even for only 1 methanol molecule per 10 000 water molecules, the maximum uptake rate of propane into CHs is enhanced and the initiation pressure is reduced. These results enable more efficient production of CHs for gas storage. This remarkable acceleration of the CH formation reaction by small quantities of methanol may place constraints on the mechanism of the inhibition effect observed under other conditions, usually employing much larger quantities of methanol. PMID:27275862

  2. Phase behavior and hydration of silk fibroin.

    Science.gov (United States)

    Sohn, Sungkyun; Strey, Helmut H; Gido, Samuel P

    2004-01-01

    The osmotic stress method was applied to study the thermodynamics of supramolecular self-assembly phenomena in crystallizable segments of Bombyx mori silkworm silk fibroin. By controlling compositions and phases of silk fibroin solution, the method provided a means for the direct investigation of microscopic and thermodynamic details of these intermolecular interactions in aqueous media. It is apparent that as osmotic pressure increases, silk fibroin molecules are crowded together to form silk I structure and then with further increase in osmotic pressure become an antiparallel beta-sheet structure, silk II. A partial ternary phase diagram of water-silk fibroin-LiBr was constructed based on the results. The results provide quantitative evidence that the silk I structure must contain water of hydration. The enhanced control over structure and phase behavior using osmotic stress, as embodied in the phase diagram, could potentially be utilized to design a new route for water-based wet spinning of regenerated silk fibroin.

  3. Influence of Physical Activity and Ambient Temperature on Hydration: The European Hydration Research Study (EHRS).

    Science.gov (United States)

    Mora-Rodriguez, Ricardo; Ortega, Juan F; Fernandez-Elias, Valentin E; Kapsokefalou, Maria; Malisova, Olga; Athanasatou, Adelais; Husemann, Marlien; Domnik, Kirsten; Braun, Hans

    2016-01-01

    This study explored the effects of physical activity (PA) and ambient temperature on water turnover and hydration status. Five-hundred seventy three healthy men and women (aged 20-60 years) from Spain, Greece and Germany self-reported PA, registered all food and beverage intake, and collected 24-h urine during seven consecutive days. Fasting blood samples were collected at the onset and end of the study. Food moisture was assessed using nutritional software to account for all water intake which was subtracted from daily urine volume to allow calculation of non-renal water loss (i.e., mostly sweating). Hydration status was assessed by urine and blood osmolality. A negative association was seen between ambient temperature and PA (r = -0.277; p < 0.001). Lower PA with high temperatures did not prevent increased non-renal water losses (i.e., sweating) and elevated urine and blood osmolality (r = 0.218 to 0.163 all p < 0.001). When summer and winter data were combined PA was negatively associated with urine osmolality (r = -0.153; p = 0.001). Our data suggest that environmental heat acts to reduce voluntary PA but this is not sufficient to prevent moderate dehydration (increased osmolality). On the other hand, increased PA is associated with improved hydration status (i.e., lower urine and blood osmolality). PMID:27128938

  4. Influence of Physical Activity and Ambient Temperature on Hydration: The European Hydration Research Study (EHRS

    Directory of Open Access Journals (Sweden)

    Ricardo Mora-Rodriguez

    2016-04-01

    Full Text Available This study explored the effects of physical activity (PA and ambient temperature on water turnover and hydration status. Five-hundred seventy three healthy men and women (aged 20–60 years from Spain, Greece and Germany self-reported PA, registered all food and beverage intake, and collected 24-h urine during seven consecutive days. Fasting blood samples were collected at the onset and end of the study. Food moisture was assessed using nutritional software to account for all water intake which was subtracted from daily urine volume to allow calculation of non-renal water loss (i.e., mostly sweating. Hydration status was assessed by urine and blood osmolality. A negative association was seen between ambient temperature and PA (r = −0.277; p < 0.001. Lower PA with high temperatures did not prevent increased non-renal water losses (i.e., sweating and elevated urine and blood osmolality (r = 0.218 to 0.163 all p < 0.001. When summer and winter data were combined PA was negatively associated with urine osmolality (r = −0.153; p = 0.001. Our data suggest that environmental heat acts to reduce voluntary PA but this is not sufficient to prevent moderate dehydration (increased osmolality. On the other hand, increased PA is associated with improved hydration status (i.e., lower urine and blood osmolality.

  5. RESEARCH ON COUPLED RELATIONSHIP BETWEEN HYDRATION NUMBER WITH RAMAN SPECTRUM

    Institute of Scientific and Technical Information of China (English)

    LEI Huaiyan; LIU Zhihong; FAN Shuanshi; XU Maoquan; GUAN Baocong

    2003-01-01

    As we know, there are three structures-sⅠ, sⅡ, and sH, with hydrocarbonate gas hydrate.Because of those special structures characteristics and potentail large fossil energy resource, gas hydrate play an important role in natural carbonate cycle system. In this paper, CH4, CO2, C3H8, and CH4 +CO2 system have been experimental performed in order to model hydrate formation and discomposition and to obtain hydrate stability conditions of tempreature and pressure. The results from laboratory using Raman spectra show that Raman spectrascopy is a effective tool to identify hydrate structure. Raman spectra of clathrate hydrate guest molecules are presented for two structure (sⅠ and sⅡ) in the following systems: CH4, CO2, C3 H8. Relatively occupancy of CH4 in the large and small cavities of sⅠ were determined by deconvoluting the v1 symmetric bands, resulting in hydration numbers of 6.04±0.03. The freqyuency of the v1 bands for CH4 in structures Ⅰ and Ⅱ differ statistically. The large cavities were measured to be almost fully occupied by CH4 and CO2, whereas only a small fraction of the small cavities are occupied by CH4. No CO2 was found in the small cavities.

  6. Determination of hydration film thickness using atomic force microscopy

    Institute of Scientific and Technical Information of China (English)

    PENG Changsheng; SONG Shaoxian; GU Qingbao

    2005-01-01

    Dispersion of a solid particle in water may lead to the formation of hydration film on the particle surface, which can strongly increase the repulsive force between the particles and thus strongly affect the stability of dispersions. The hydration film thickness, which varies with the variation of property of suspension particles, is one of the most important parameters of hydration film, and is also one of the most difficult parameters that can be measured accurately. In this paper, a method, based on force-distance curve of atomic force microscopy, for determining the hydration film thickness of particles is developed. The method utilizes the difference of cantilever deflection before, between and after penetrating the hydration films between tip and sample, which reflect the difference of slope on the force-distance curve. 3 samples, mica, glass and stainless steel, were used for hydration thickness determination, and the results show that the hydration film thickness between silicon tip and mica, glass and stainless steel are 30.0(2.0, 29.0(1.0 and 32.5(2.5 nm, respectively.

  7. Physical modeling of the formation of clathrate hydrates of methane

    Science.gov (United States)

    Drobyshev, A.; Aldiyarov, A.; Kurnosov, V.; Katpaeva, K.; Korshikov, E.; Sokolov, D.; Shinbayeva, A.; Timchenko, A.

    2015-06-01

    Nowadays natural gas hydrates attract special attention as a possible source of fossil fuel. According to various estimates, the reserves of hydrocarbons in hydrates exceed considerably explored reserves of natural gas. Due to the clathrate structure the unit volume of the gas hydrate can contain up to 160-180 volumes of pure gas. In recent years interest to a problem of gas hydrates has considerably increased. Such changes are connected with the progress in searches of the alternative sources of hydrocarbonic raw materials in countries that do not possess the resources of energy carriers. Thus gas hydrates are nonconventional sources of the hydrocarbonic raw materials which can be developed in the near future. At the same time, mechanisms of methane clathrate hydrates formations have not reached an advanced level, their thermophysical and mechanical properties have not been investigated profoundly. Thereby our experimental modeling of the processes of formation of methane clathrate hydrates in water cryomatrix prepared by co-condensation from the gas phase onto a cooled substrate was carried out over the range of condensation temperatures 12-60 K and pressures 10-4-10-6 Torr. In our experiments the concentration of methane in water varied in the range of 5%-90%. The thickness deposited films was 30-60 μm. The vibrational spectra of two-component thin films of CH4 + H2O condensates were measured and analyzed.

  8. Detecting gas hydrate behavior in crude oil using NMR.

    Science.gov (United States)

    Gao, Shuqiang; House, Waylon; Chapman, Walter G

    2006-04-01

    Because of the associated experimental difficulties, natural gas hydrate behavior in black oil is poorly understood despite its grave importance in deep-water flow assurance. Since the hydrate cannot be visually observed in black oil, traditional methods often rely on gas pressure changes to monitor hydrate formation and dissociation. Because gases have to diffuse through the liquid phase for hydrate behavior to create pressure responses, the complication of gas mass transfer is involved and hydrate behavior is only indirectly observed. This pressure monitoring technique encounters difficulties when the oil phase is too viscous, the amount of water is too small, or the gas phase is absent. In this work we employ proton nuclear magnetic resonance (NMR) spectroscopy to observe directly the liquid-to-solid conversion of the water component in black oil emulsions. The technique relies on two facts. The first, well-known, is that water becomes essentially invisible to liquid state NMR as it becomes immobile, as in hydrate or ice formation. The second, our recent finding, is that in high magnetic fields of sufficient homogeneity, it is possible to distinguish water from black oil spectrally by their chemical shifts. By following changes in the area of the water peak, the process of hydrate conversion can be measured, and, at lower temperatures, the formation of ice. Taking only seconds to accomplish, this measurement is nearly direct in contrast to conventional techniques that measure the pressure changes of the whole system and assume these changes represent formation or dissociation of hydrates - rather than simply changes in solubility. This new technique clearly can provide accurate hydrate thermodynamic data in black oils. Because the technique measures the total mobile water with rapidity, extensions should prove valuable in studying the dynamics of phase transitions in emulsions. PMID:16570953

  9. Hydration of calcium sulfoaluminate cements - Experimental findings and thermodynamic modelling

    International Nuclear Information System (INIS)

    Calcium sulfoaluminate cements (CSA) are a promising low-CO2 alternative to ordinary Portland cements and are as well of interest concerning their use as binder for waste encapsulation. In this study, the hydration of two CSA cements has been investigated experimentally and by thermodynamic modelling between 1 h and 28 days at w/c ratios of 0.72 and 0.80, respectively. The main hydration product of CSA is ettringite, which precipitates together with amorphous Al(OH)3 until the calcium sulfate is consumed after around 1-2 days of hydration. Afterwards, monosulfate is formed. In the presence of belite, straetlingite occurs as an additional hydration product. The pore solution analysis reveals that straetlingite can bind a part of the potassium ions, which are released by the clinker minerals. The microstructure of both cements is quite dense even after 16 h of hydration, with not much pore space available at a sample age of 28 days. The pore solution of both cements is dominated during the first hours of hydration by potassium, sodium, calcium, aluminium and sulfate; the pH is around 10-11. When the calcium sulfate is depleted, the sulfate concentration drops by a factor of 10. This increases pH to around 12.5-12.8. Based on the experimental data, a thermodynamic hydration model for CSA cements based on cement composition, hydration kinetics of clinker phases and calculations of thermodynamic equilibria by geochemical speciation has been established. The modelled phase development with ongoing hydration agrees well with the experimental findings.

  10. Kinetics of bread crumb hydration as related to porous microstructure.

    Science.gov (United States)

    Mathieu, Vincent; Monnet, Anne-Flore; Jourdren, Solenne; Panouillé, Maud; Chappard, Christine; Souchon, Isabelle

    2016-08-10

    During oral processing and throughout the digestion process, hydration mechanisms have a key influence on the functional properties of food. This is the case with bread, for which hydration may affect the kinetics of starch hydrolysis as well as taste, aroma and texture perceptions. In this context, the aim of the present study is to understand how crumb porous micro-architecture impacts hydration kinetics. Four types of French baguettes were considered, varying in structure and/or compositions. An experimental set-up was developed for the real-time measurement of water uptake in crumb samples. Mathematical models were then fitted to extract quantitative parameters of use for the description and the understanding of experimental observations. Finally, bread crumb samples were analyzed before and after hydration through X-ray micro-computed tomography for the assessment of crumb micro-architectural properties. Distinct hydration behaviors were observed for the four types of bread. Higher hydration rates and capacities were reported for industrial baguettes (highest porosity) compared to denser semi-industrial, whole wheat and traditional baguettes. However, crumb porosity alone is not sufficient to predict hydration behavior. This study made it possible to point out the importance of capillary action in crumb hydration mechanisms, with a strong role of cells with diameters of 2 mm and below. The high density of these small cells generates high interconnection probabilities that may have an impact both on crumb hydration duration and capacity. As a consequence, accounting for microstructural features resulting from bread formulation may provide useful leverages for the control of functional properties. PMID:27466974

  11. Oxygen-18 enrichment in the water of a clathrate hydrate

    Energy Technology Data Exchange (ETDEWEB)

    Davidson, D.W.; Leaist, D.G. (National Research Council of Canada, Ottawa, Ontario. Div. of Chemistry); Hesse, R. (McGill Univ., Montreal, Quebec (Canada). Dept of Geological Sciences)

    1983-12-01

    The equilibrium constants for the fractionation of H/sub 2//sup 18/O and H/sub 2//sup 16/O between liquid and solid phases were determined by slow freezing of ice and by slow formation of the clathrate hydrate of tetrahydrofuran from liquid solution. Both systems gave ..cap alpha.. = 1.0026/sub 8/. It is likely that oxygen-18 enrichment of the water in clathrate hydrates generally is essentially the same as for ice and that the relatively high oxygen-18 content observed in pore waters from some deep-sea sediments arises from the recent presence of methane hydrate.

  12. 3-D numerical modeling of methane hydrate deposits

    OpenAIRE

    Pinero, Elena; W. Rottke; Fuchs, T.; Hensen, Christian; Haeckel, Matthias; Wallmann, Klaus

    2011-01-01

    Within the German gas hydrate initiative SUGAR, we have developed a new tool for predicting the formation of sub-seafloor gas hydrate deposits. For this purpose, a new 2D/3D module simulating the biogenic generation of methane from organic material and the formation of gas hydrates has been added to the petroleum systems modeling software package PetroMod®. T ypically, PetroMod® simulates the thermogenic generation of multiple hydrocarbon components including oil and gas, their migration t...

  13. Inhibition of Methane Hydrate Formation by Ice-Structuring Proteins

    DEFF Research Database (Denmark)

    Jensen, Lars; Ramløv, Hans; Thomsen, Kaj;

    2010-01-01

    investigated. Thermal hysteresis ice formation experiments revealed that ISP from Tenebrio molitor causes higher thermal hysteresis for ice formation compared to type III ISP identified in ocean pout while PVP did not cause thermal hysteresis. This indicates that there might be a direct relationship between......, assumed biodegradable, are capable of inhibiting the growth of methane hydrate (a structure I hydrate). The ISPs investigated were type III HPLC12 (originally identified in ocean pout) and ISP type III found in meal worm (Tenebrio molitor). These were compared to polyvinylpyrrolidone (PVP) a well...... ISP performance for ice and hydrate inhibition, and that thermal hysteresis experiments can be used to screen ISPs as kinetic inhibitors....

  14. Effect on Hydration and Hardening of Tricalcium Phosphate Bone Cement

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The bioactive α-Ca3 (PO4)2 bone cement was studied by XRD , SEM and isothermal calorimetric measurements. The results showed that a mixed pattern of TCP and hydroxylapatite were obtained after hydration and hardening. The mechanism of hydration and hardening of the α-Ca3 ( PO4 )2 was dissolution-precipitation,(NH4) H2 PO4 was the best set accelerator to the α-Ca3 ( PO4 )2 cement, and the HAP powers and the(NH4) H2 PO4 concentration had a great effect on the hydration rate of α-Ca3 ( PO4 )2.

  15. The growth rate of gas hydrate from refrigerant R12

    Energy Technology Data Exchange (ETDEWEB)

    Kendoush, Abdullah Abbas; Jassim, Najim Abid [Centre of Engineering Physics, Ministry of Sciences and Technology, P.O. Box 765, Baghdad (Iraq); Joudi, Khalid A. [Al-Nahrain University, Baghdad (Iraq)

    2006-07-15

    Experimental and theoretical investigations were presented dealing with three phase direct-contact heat transfer by evaporation of refrigerant drops in an immiscible liquid. Refrigerant R12 was used as the dispersed phase, while water and brine were the immiscible continuous phase. A numerical solution is presented to predict the formation rate of gas hydrates in test column. The solution provided an acceptable agreement when compared with experimental results. The gas hydrate growth rate increased with time. It increased with increasing dispersed phase flow rate. The presence of surface-active sodium chloride in water had a strong inhibiting effect on the gas hydrate formation rate. (author)

  16. Experimental studies for the cyclability of salt hydrates for thermochemical heat storage

    NARCIS (Netherlands)

    Donkers, P.A.J.; Pel, L.; Adan, O.C.G.

    2016-01-01

    Salt hydrates have promising potential as heat storage materials by use of their hydration/dehydration reaction. These hydration/dehydration reactions are studied in this paper for CuCl2, CuSO4, MgCl2 and MgSO4. During a hydration/dehydration reaction, the salt shrinks and expands as a result of the

  17. Formation of natural gas hydrates in marine sediments 1. Conceptual model of gas hydrate growth conditioned by host sediment properties

    Science.gov (United States)

    Clennell, M.B.; Hovland, M.; Booth, J.S.; Henry, P.; Winters, W.J.

    1999-01-01

    The stability of submarine gas hydrates is largely dictated by pressure and temperature, gas composition, and pore water salinity. However, the physical properties and surface chemistry of deep marine sediments may also affect the thermodynamic state, growth kinetics, spatial distributions, and growth forms of clathrates. Our conceptual model presumes that gas hydrate behaves in a way analogous to ice in a freezing soil. Hydrate growth is inhibited within fine-grained sediments by a combination of reduced pore water activity in the vicinity of hydrophilic mineral surfaces, and the excess internal energy of small crystals confined in pores. The excess energy can be thought of as a "capillary pressure" in the hydrate crystal, related to the pore size distribution and the state of stress in the sediment framework. The base of gas hydrate stability in a sequence of fine sediments is predicted by our model to occur at a lower temperature (nearer to the seabed) than would be calculated from bulk thermodynamic equilibrium. Capillary effects or a build up of salt in the system can expand the phase boundary between hydrate and free gas into a divariant field extending over a finite depth range dictated by total methane content and pore-size distribution. Hysteresis between the temperatures of crystallization and dissociation of the clathrate is also predicted. Growth forms commonly observed in hydrate samples recovered from marine sediments (nodules, and lenses in muds; cements in sands) can largely be explained by capillary effects, but kinetics of nucleation and growth are also important. The formation of concentrated gas hydrates in a partially closed system with respect to material transport, or where gas can flush through the system, may lead to water depletion in the host sediment. This "freeze-drying" may be detectable through physical changes to the sediment (low water content and overconsolidation) and/or chemical anomalies in the pore waters and metastable

  18. Low-δD hydration rinds in Yellowstone perlites record rapid syneruptive hydration during glacial and interglacial conditions

    Science.gov (United States)

    Bindeman, Ilya N.; Lowenstern, Jacob B.

    2016-01-01

    Hydration of silicic volcanic glass forms perlite, a dusky, porous form of altered glass characterized by abundant “onion-skin” fractures. The timing and temperature of perlite formation are enigmatic and could plausibly occur during eruption, during post-eruptive cooling, or much later at ambient temperatures. To learn more about the origin of natural perlite, and to fingerprint the hydration waters, we investigated perlitic glass from several synglacial and interglacial rhyolitic lavas and tuffs from the Yellowstone volcanic system. Perlitic cores are surrounded by a series of conchoidal cracks that separate 30- to 100-µm-thick slivers, likely formed in response to hydration-induced stress. H2O and D/H profiles confirm that most D/H exchange happens together with rapid H2O addition but some smoother D/H variations may suggest separate minor exchange by deuterium atom interdiffusion following hydration. The hydrated rinds (2–3 wt% H2O) transition rapidly (within 30 µm, or by 1 wt% H2O per 10 µm) to unhydrated glass cores. This is consistent with quenched “hydration fronts” where H2O diffusion coefficients are strongly dependent on H2O concentrations. The chemical, δ18O, and δD systematics of bulk glass records last equilibrium between ~110 and 60 °C without chemical exchange but with some δ18O exchange. Similarly, the δ18O of water extracted from glass by rapid heating suggests that water was added to the glass during cooling at C. Our observations support fast hydration at temperatures as low as 60 °C; prolonged exposure to high temperature of 175°–225° during water addition is less likely as the glass would lose alkalies and should alter to clays within days. A compilation of low-temperature hydration diffusion coefficients suggests ~2 orders of magnitude higher rates of diffusion at 60–110 °C temperatures, compared with values expected from extrapolation of high-temperature (>400 °C) experimental data. The thick hydration

  19. Early hydration cement Effect of admixtures superplasticizers

    Directory of Open Access Journals (Sweden)

    Puertas, F.

    2001-06-01

    Full Text Available Early hydration of portland cement with superplasticizer admixtures of different nature has been studied. These admixtures were: one based on melamine synthetic, other based on vinyl copolymer and other based on polyacrylate copolymers. The dosage of the formers were constant (1% weigth of cement and for the third, the influence of admixture dosage was also evaluated, giving dosage values among 1-0.3%. The pastes obtained were studied by conduction calorimetry, XRD and FTIR. Also the apparent fluidity was determined by "Minislump" test. The main results obtained were: a superplasticizers admixtures used, regardless of their nature and for the polycarboxilate one the dosage, retard the silicate hydration (specially, alite phase, b The ettringite formation is affected by the nature of the admixture. cA relationship between the dosage of admixture based on polycarboxilates and the time at the acceleration has been established. A lineal relation (y = 11.03 + 16.05x was obtained. From these results is possible to know, in function of dosage admixture, the time when the masive hydration products and the setting times are produced. Also the total heat releases in these reactions is independent of the nature and dosage of admixture, saying that in all cases the reactions are the same.

    En el presente trabajo se ha estudiado la hidratación inicial de un cemento portland aditivado con superplastificantes de diferente naturaleza. Dichos aditivos fueron: uno basado en melaminas sintéticas, otro en copolímeros vinilicos y otro en policarboxilatos. La dosificación de los dos primeros se fijó constante en 1% en peso con relación al cemento, mientras que para el tercero se evaluó, también, la influencia de la dosificación, tomando proporciones desde el 1% hasta el 0,3%. Las pastas obtenidas se estudiaron por: calorimetría de conducción, DRX y FTIR. También se determinó la fluidez de la pasta a través del ensayo del "Minislump ". Los

  20. Influence of Cellulose Ethers on Hydration Products of Portland Cement

    Institute of Scientific and Technical Information of China (English)

    MA Baoguo; OU Zhihua; JIAN Shouwei; XU Rulin

    2011-01-01

    Cellulose ethers are widely used to mortar formulations, and it is significant to understand the interaction between cellulose ethers and cement pastes. FT-IR spectra, thermal analysis and SEM are used to investigate hydration products in the cement pastes modified by HEMC and HPMC in this article. The results show that the hydration products in modified cement pastes were finally identical with those in the unmodified cement paste, but the major hydration products, such as CH (calcium hydroxide), ettringite and C-S-H, appeared later in the modified cement pastes than in the unmodified cement paste. The cellulose ethers decrease the outer products and increase inner products of C-S-H gels. Compared to unmodified cement pastes, no new products are found in the modified cement pastes in the present experiment. The HEMC and HPMC investigation shows almost the same influence on the hydration products of Portland cement.

  1. [Nutrition and hydration at the end of life].

    Science.gov (United States)

    Devalois, Bernard; Broucke, Marion

    2015-04-01

    At the end of life the pleasure function of alimentation is to be preferred to its nutritive function. Artificial nutrition and hydration in an enteral or parenteral way are artificial life support techniques. Artificial nutrition and hydration are systematically justified for patients in curative phase that require it but not for patients in a terminal or agonal phase. The fear of death from hunger and thirst is not justified. It is more relevant of a symbolic and phantasmic dimension than of an objective reality. The practice of oral care is much more effective than installing an artificial hydration to improve the comfort of a patient at the very end of life. Withdrawing or withholding an artificial nutrition and hydration can prevent an unreasonable obstinacy prohibited by law. PMID:25823829

  2. China Has Great Potential for Tapping Natural Gas Hydrate

    Institute of Scientific and Technical Information of China (English)

    Shang Yingtao

    2010-01-01

    @@ China has successfully excavated natural gas hydrate,in permanent tundra in the south margin of the country's northwestern Qilian Mountains,according to the information recently made available from China's Ministry of Land and Resources.

  3. Methane hydrates and the future of natural gas

    Science.gov (United States)

    Ruppel, Carolyn

    2011-01-01

    For decades, gas hydrates have been discussed as a potential resource, particularly for countries with limited access to conventional hydrocarbons or a strategic interest in establishing alternative, unconventional gas reserves. Methane has never been produced from gas hydrates at a commercial scale and, barring major changes in the economics of natural gas supply and demand, commercial production at a large scale is considered unlikely to commence within the next 15 years. Given the overall uncertainty still associated with gas hydrates as a potential resource, they have not been included in the EPPA model in MITEI’s Future of Natural Gas report. Still, gas hydrates remain a potentially large methane resource and must necessarily be included in any consideration of the natural gas supply beyond two decades from now.

  4. Clinical study on orofacial photonic hydration using phototherapy and biomaterials

    Science.gov (United States)

    Lizarelli, Rosane F. Z.; Grandi, Natália D. P.; Florez, Fernando L. E.; Grecco, Clovis; Lopes, Luciana A.

    2015-06-01

    Skin hydration is important to prevent aging and dysfunction of orofacial system. Nowadays, it is known that cutaneous system is linked to muscle system, then every dentist need to treat healthy facial skin, as lips, keeping orofacial functions healthy. Thirty-two patients were treated using laser and led therapy single or associated to biomaterials (dermo-cosmetics) searching for the best protocol to promote skin hydration. Using a peace of equipment to measure electric impedance, percentage of water and oil from skin, before and after different treatments were analyzed. Statistic tests using 5% and 0.1% of significance were applied and results showed that light could improve hydration of epidermis layer of facial skin. Considering just light effect, using infrared laser followed by blue led system is more effective to hydration than just blue led system application. Considering dermo-cosmetic and light, the association between both presented the best result.

  5. The hydration/dehydration behavior of aspartame revisited.

    Science.gov (United States)

    Guguta, C; Meekes, H; de Gelder, R

    2008-03-13

    Aspartame, l-aspartyl-l-phenylalanine methyl ester, has two hydrates (IA and IB), a hemi-hydrate (IIA) and an anhydrate (IIB). The hydration/dehydration behavior of aspartame was investigated using hot-humidity stage X-ray powder diffraction (XRPD) and molecular mechanics modeling in combination with differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The results of this study are compared to earlier studies on aspartame as described in literature. It is shown that earlier transition studies were hampered by incomplete conversions and wrong assignment of the forms. The combination of the techniques applied in this study now shows consistent results for aspartame and yields a clear conversion scheme for the hydration/dehydration behavior of the four forms.

  6. Infrared spectroscopy for monitoring gas hydrates in aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Dobbs, G.T.; Luzinova, Y.; Mizaikoff, B. [Georgia Inst. of Technology, Atlanta, GA (United States). School of Chemistry and Biochemistry; Raichlin, Y.; Katzir, A. [Tel-Aviv Univ., Tel-Aviv (Israel). Shool of Physics and Astronomy

    2008-07-01

    This paper introduced the first principles for monitoring gas hydrate formation and dissociation in aqueous solution by evaluating state-responsive infrared (IR) absorption features of water with fiberoptic evanescent field spectroscopy. A first order linear functional relationship was also derived according to Lambert Beer's law in order to quantify the percentage gas hydrate within the volume of water probed via the evanescent field. In addition, spectroscopic studies evaluating seafloor sediments collected from a gas hydrate site in the Gulf of Mexico revealed minimal spectral interferences from sediment matrix components. As such, evanescent field sensing strategies were established as a promising perspective for monitoring the dynamics of gas hydrates in oceanic environments. 21 refs., 5 figs.

  7. Interaction Study of Guest with Host in Clathrate Hydrate

    Institute of Scientific and Technical Information of China (English)

    Lin Wang; Shunle Dong

    2007-01-01

    Lattice dynamical simulations of noble gas hydrate structures I and II have been performed. Potential energies were investigated to study the influence of guest species on the stability of the hydrate structure. Results show that when the diameter of inclusion molecules is between 3 A and 4.2 A, such as Ar and Kr, the critical role of the 512 cage in the stabilization of hydrates becomes effective. For Xe hydrates SI and SII, with the help of lattice dynamical calculations, the modes attributions are identified directly. We proposed the resonant effect of the fingerprint frequency at about 7 meV and 10 meV which arise from the coupling of Xe molecules in the 512 cage with the host lattice.

  8. Gas hydrates in Krishna-Godavari offshore basin

    Digital Repository Service at National Institute of Oceanography (India)

    Ramprasad, T.; Mazumdar, A.; Dewangan, P.

    The huge demand of energy fuels in the country poses a large burden on the exchequer. Augmenting the demand with the non conventional energy fuels is becoming inevitable. Pure form of Methane from gas hydrate deposits could be a potential...

  9. Effect of Bed Deformation on Natural Gas Production from Hydrates

    Directory of Open Access Journals (Sweden)

    Mohamed Iqbal Pallipurath

    2013-01-01

    Full Text Available This work is based on modelling studies in an axisymmetric framework. The thermal stimulation of hydrated sediment is taken to occur by a centrally placed heat source. The model includes the hydrate dissociation and its effect on sediment bed deformation and resulting effect on gas production. A finite element package was customized to simulate the gas production from natural gas hydrate by considering the deformation of submarine bed. Three sediment models have been used to simulate gas production. The effect of sediment deformation on gas production by thermal stimulation is studied. Gas production rate is found to increase with an increase in the source temperature. Porosity of the sediment and saturation of the hydrate both have been found to significantly influence the rate of gas production.

  10. Ion-water clusters, bulk medium effects, and ion hydration

    CERN Document Server

    Merchant, Safir; Dean, Kelsey R; Asthagiri, D

    2011-01-01

    Thermochemistry of gas-phase ion-water clusters together with estimates of the hydration free energy of the clusters and the water ligands are used to calculate the hydration free energy of the ion. Often the hydration calculations use a continuum model of the solvent. The primitive quasichemical approximation to the quasichemical theory provides a transparent framework to anchor such efforts. Here we evaluate the approximations inherent in the primitive quasichemical approach and elucidate the different roles of the bulk medium. We find that the bulk medium can stabilize configurations of the cluster that are usually not observed in the gas phase, while also simultaneously lowering the excess chemical potential of the ion. This effect is more pronounced for soft ions. Since the coordination number that minimizes the excess chemical potential of the ion is identified as the optimal or most probable coordination number, for such soft ions, the optimum cluster size and the hydration thermodynamics obtained with...

  11. Multicomponent seismic forward modeling of gas hydrates beneath the seafloor

    Institute of Scientific and Technical Information of China (English)

    Yang Jia-Jia; He Bing-Shou; Zhang Jian-Zhong

    2014-01-01

    We investigated the effect of microscopic distribution modes of hydrates in porous sediments, and the saturation of hydrates and free gas on the elastic properties of saturated sediments. We simulated the propagation of seismic waves in gas hydrate-bearing sediments beneath the seafloor, and obtained the common receiver gathers of compressional waves (P-waves) and shear waves (S-waves). The numerical results suggest that the interface between sediments containing gas hydrates and free gas produces a large-amplitude bottom-simulating reflector. The analysis of multicomponent common receiver data suggests that ocean-bottom seismometers receive the converted waves of upgoing P-and S-waves, which increases the complexity of the wavefield record.

  12. Effect of Impeller Agitation on Preparation of Tetra-n-Butyl Ammonium Bromide Semiclathrate Hydrate Slurries

    OpenAIRE

    Yoshiro Inoue; Kazunari Ohgaki; Shunsuke Hashimoto; Hiroyuki Ito

    2012-01-01

    The slurries-containing tetra-n-butyl ammonium bromide (TBAB) solution and its semiclathrate hydrate have attracted a lot of interest as latent heat transport media. These hydrate slurries contain some microparticles of crystal, and the size and shape of these hydrate particles could affect the mobility of slurries. Hence, it is essential to investigate the efficient hydrate-slurry preparation methods and the effect of hydrate particles on the fluid property of slurries for the application to...

  13. EXPERIMENTAL INVESTIGATION ON GAS HYDRATE FORMATION IN PRESENCE OF ADDITIVE COMPONENTS

    Institute of Scientific and Technical Information of China (English)

    SUN Zhigao; FAN Shuanshi; GUO Kaihua

    2003-01-01

    Additives were used to increase gas hydrate formation rate and storage capacity. Experimental tests of methane hydrate formation were carried out in surfactant water solutions in a high-pressure cell.Sodium dodecyl sulfate (SDS) and alkyl polysaccharide glycoside (APG) were used to increase hydrate formation. The effect of SDS on hydrate formation is more pronounced compared APG. Cyclopentane (CP) also improves hydrate formation rates while it cannot increase methane gas storage capacity.

  14. The chemistry of low dosage clathrate hydrate inhibitors.

    OpenAIRE

    Perrin, A.; Musa, O. M.; STEED, J. W.

    2013-01-01

    This review aims to introduce the chemistry of low dosage inhibitors of clathrate hydrate formation within the context of their role in the oil and gas industry. The review covers both kinetic hydrate inhibitors and anti-agglomerants from the point of view of structure–function relationships, focussing on recent refinements in mechanistic understanding and chemical design, and the consequently evolving and increasingly fine-tuned properties of these fascinating compounds.

  15. Evolution of the hydration in cements with additions

    OpenAIRE

    Bonavetti, V. L.; Rahhal, V. F.; Irassar, E. F.

    2002-01-01

    In this paper, the hydration mechanism of portland cement pastes with limestone, quartz and natural pozzolan (80/20 weight) was analized. The techniques used were nonevaporable water content, pozzolanic activity and X-ray diffraction. Results show that filler effect increases initially the amount of hydration products in all pastes. For limestone pastes, the dilution effect is significant at long time, for quartz and pozzolan pastes the dilution effect was lower due to the contribution of the...

  16. Hydration process of nuclear-waste glass: an interim report

    International Nuclear Information System (INIS)

    Aging of simulated nuclear waste glass by contact with a controlled-temperature, humid atmosphere results in the formation of a double hydration layer penetrating the glass, as well as the formation of minerals on the glass surface. The hydration process can be described by Arrhenius behavior between 120 and 2400C. Results suggest that simulated aging reactions are necessary for demonstrating that nuclear waste forms can meet projected Nuclear Regulatory Commission regulations. 16 figures, 4 tables

  17. Methane hydrates in marine sediments - Untapped source of energy

    Digital Repository Service at National Institute of Oceanography (India)

    Jauhari, P.

    in oil and gas pipelines for clogging the lines, methane hydrates are now looked upon as a promising alternate resource of energy. Natural gas is expected to play an important role in power generation and vehicular transportation because... of the industry in 1930s when it was realised that the long distance oil and gas transmission pipelines in the USA were being clogged by the formation of gas hydrates within the pipelines. To overcome this problem, researches were done on the composition...

  18. Chemical characteristics of mineral trioxide aggregate and its hydration reaction

    OpenAIRE

    Chang, Seok-Woo

    2012-01-01

    Mineral trioxide aggregate (MTA) was developed in early 1990s and has been successfully used for root perforation repair, root end filling, and one-visit apexification. MTA is composed mainly of tricalcium silicate and dicalcium silicate. When MTA is hydrated, calcium silicate hydrate (CSH) and calcium hydroxide is formed. Formed calcium hydroxide interacts with the phosphate ion in body fluid and form amorphous calcium phosphate (ACP) which finally transforms into calcium deficient hydroxyap...

  19. Hydration studies of calcium sulfoaluminate cements blended with fly ash

    OpenAIRE

    Garcia-Maté, Marta; De la Torre, Angeles G; León-Reina, Laura; Aranda, Miguel A. G.; Santacruz, Isabel

    2013-01-01

    The main objective of this work is to study the hydration and properties of calciumsulfoaluminate cement pastes blended with fly ash (FA) and the corresponding mortars at different hydration ages. Laboratory X-ray powder diffraction, rheological studies, thermal analysis, porosimetry and compressive strength measurements were performed. The analysis of the diffraction data by Rietveld method allowed quantifying crystalline phases and overall amorphous contents. The studied paramet...

  20. Numerical modeling of gas hydrate emplacements in oceanic sediments

    OpenAIRE

    Schnurle, Philippe; Liu, Char-Shine

    2011-01-01

    We have implemented a 2-dimensional numerical model for simulating gas hydrate and free gas accumulation in marine sediments. The starting equations are those of the conservation of the transport of momentum, energy, and mass, as well as those of the thermodynamics of methane hydrate stability and methane solubility in the pore-fluid. These constitutive equations are then integrated into a finite element in space, finite-difference in time scheme. We are then able to examine the formation and...

  1. Hydration effects of deoxyadenosine: A differential calorimetric study

    Science.gov (United States)

    Cooper, Robert; Lee, S. A.; Griffey, R. H.; Mohan, V.

    2000-03-01

    The water of hydration is an integral part of the double helical structure of DNA. In order to understand the interactions between water and DNA, we have studied the hydration of the nucleoside deoxyadenosine as a function of relative humidity. Differential scanning calorimetry was used to measure the enthalpy and activation energy of dehydration. These data will be contrasted with the results obtained from guanosine and deoxyguanosine.

  2. Formation of nitric acid hydrates - A chemical equilibrium approach

    Science.gov (United States)

    Smith, Roland H.

    1990-01-01

    Published data are used to calculate equilibrium constants for reactions of the formation of nitric acid hydrates over the temperature range 190 to 205 K. Standard enthalpies of formation and standard entropies are calculated for the tri- and mono-hydrates. These are shown to be in reasonable agreement with earlier calorimetric measurements. The formation of nitric acid trihydrate in the polar stratosphere is discussed in terms of these equilibrium constants.

  3. Oceanic methane hydrates: untapped fossil-fuel reservoirs

    International Nuclear Information System (INIS)

    Years ago, oil explorers had only a superficial idea about the existence of a solid form of natural gas known as methane hydrate, and much less, about its geological mode of occurrence. Intensive explorations undertaken by oceanographers and oil geologists, during the last ten years, many occurrences around the world have come to light. Today, hydrate reserves are supposed to hold more fossil fuel energy than is present in conventional oil, gas and coal deposits

  4. Rheological and hydration characterization of calcium sulfoaluminate cement pastes

    OpenAIRE

    García-Maté, Marta; Santacruz, Isabel; de la Torre, Ángeles G.; León-Reina, Laura; Aranda, Miguel A. G.

    2012-01-01

    Calcium sulfoaluminate (CSA) cements are currently receiving a lot of attention because their manufacture produces less CO2 than ordinary Portland cement (OPC). However, it is essential to understand all parameters which may affect the hydration processes. This work deals with the study of the effect of several parameters, such as superplasticizer (SP), gypsum contents (10, 20 and 30 wt%) and w/c ratio (0.4 and 0.5), on the properties of CSA pastes during early hydration. This characteriza...

  5. Electrical Measurement to Assess Hydration Process and the Porosity Formation

    Institute of Scientific and Technical Information of China (English)

    WEI Xiaosheng; XIAO Lianzhen; LI Zongjin

    2008-01-01

    The change of electrical resistivity with time at early ages was used to investigate the hydration process and the porosity development. Porosity reduction process of cement-based materials hydration was developed by a proposed method. The porosity reduction is fast at the setting period. The results find that the pore discontinuity occurs faster at lower water/cement ratios than at higher water/cement ratios which is similar to the results of the Percolation method.

  6. Evaluation of Hydrated Lime Filler in Asphalt Mixtures

    OpenAIRE

    Mohammed Abbas Hasan Al-Jumaily

    2008-01-01

    Mineral filler is one of important materials and affecting on properties and quality of asphalt mixtures .There are different types of mineral filler depended on cost and quality , the matter encourages us to achieve this study to evaluate hydrated lime filler effects on properties of asphalt mixes related with strength and durability. Conventional asphaltic concrete mixtures with Portland cement and soft sandstone fillers and mixtures modified with hydrated lime were evaluated for their fund...

  7. Notes on hydrated cement fractals investigated by SANS

    Energy Technology Data Exchange (ETDEWEB)

    Ficker, T [Faculty of Civil Engineering, Physics Department, Technical University, Zizkova 17, CZ-602 00 Brno (Czech Republic); Len, A [Budapest Neutron Centre, Konkoly Thege 29-33, H-1525 Budapest (Hungary); Nemec, P [Faculty of Civil Engineering, Physics Department, Technical University, Zizkova 17, CZ-602 00 Brno (Czech Republic)

    2007-07-07

    Hydrated cement pastes with different water-to-cement ratios have been investigated by the small-angle scattering neutron technique. Special attention has been paid to the fractal nanostructure of the calcium silicate hydrate (C-S-H solid gel) and its basic building particles, i.e. nanometric globules. The inner stability of these particles has been tested and shown to be sufficiently persistent to withstand all spatial regroupings of the overall nanostructure caused by variations of w/c ratios.

  8. CO2 capture by gas mixtures hydrate crystallisation

    OpenAIRE

    Bouchemoua-Benaissa, Amina; Fezoua, Amara; Ouabbas, Yamina; Chauvy, Fabien; Cameirão, Ana; Herri, Jean-Michel

    2009-01-01

    National audience CO2 capture and sequestration represent a major industrial and scientific challenge of this century. There are different methods of CO2 separation and capture, such as solide adsorption, amines adsorption and cryogenic fractionation. Although these processes are well developed at industrial level, they are energy intensive. Hydrate formation method is a less energy intensive and has an interesting potential to separate carbon dioxide (Nguyen Hong, 2007). Gas hydrates are ...

  9. Comparative measurement of hydration effects of herbal moisturizers

    OpenAIRE

    Swarnlata Saraf; Sneha Sahu; Chanchal Deep Kaur; Shailendra Saraf

    2010-01-01

    Improvements of skin hydration properties by the use of polyherbal moisturizers are the recent advances in cosmetic preparations to avoid the harmful effects of chemical moisturizers. The main aim of the study was to establish selection preference of different available marketed herbal moisturizers on the basis of the efficiency of constituents for their hydration effects. The criteria for the selection of formulations were presence of herbal constituents, wheat germ oil and Aloe vera extract...

  10. Dynamical Transition in Hydrated Biomolecules, Native and Denatured

    International Nuclear Information System (INIS)

    We use elastic neutron scattering to demonstrate that a sharp increase in the mean-squared atomic displacements, commonly observed in hydrated proteins above 200 K and often referred to as the dynamical transition, is present in the hydrated state of both native and denatured lysozyme. A direct comparison of the native and denatured protein thus confirms that the presence of the transition in the mean-squared atomic displacements is not specific to biologically functional molecules.

  11. Life Origination Hydrate Theory (LOH-Theory) and Mitosis and Replication Hydrate Theory (MRH-Theory): three-dimensional PC validation

    Science.gov (United States)

    Kadyshevich, E. A.; Dzyabchenko, A. V.; Ostrovskii, V. E.

    2014-04-01

    Size compatibility of the CH4-hydrate structure II and multi-component DNA fragments is confirmed by three-dimensional simulation; it is validation of the Life Origination Hydrate Theory (LOH-Theory).

  12. Gas hydrates: entrance to a methane age or climate threat?

    Energy Technology Data Exchange (ETDEWEB)

    Krey, Volker; Nakicenovic, Nebojsa; Grubler, Arnulf; O' Neill, Brian; Riahi, Keywan [International Institute for Applied Systems Analysis (IIASA), Schlossplatz 1, 2361 Laxenburg (Austria); Canadell, Josep G [Global Carbon Project, CSIRO Marine and Atmospheric Research, GPO Box 3023, Canberra, ACT 2601 (Australia); Abe, Yuichi [Social Science Consulting Unit, Japan Nus Co. Ltd, Loop-X Building 7F, 9-15 Kaigan 3-Chome, Minato-ku, Tokyo 108-0022 (Japan); Andruleit, Harald [Bundesanstalt fuer Geowissenschaften und Rohstoffe (BGR), Stilleweg 2, 30655 Hannover (Germany); Archer, David [Department of the Geophysical Sciences at the University of Chicago, 5734 South Ellis Avenue, Chicago, IL 60637 (United States); Hamilton, Neil T M [WWF International Arctic Programme, Kristian Augusts gate 7a, 0130 Oslo (Norway); Johnson, Arthur [Hydrate Energy International, 612 Petit Berdot Drive, Kenner, LA 70065 (United States); Kostov, Veselin [Department of Physics and Astronomy, Johns Hopkins University, 3400 N Charles Street Baltimore, MD 21218 (United States); Lamarque, Jean-Francois [Atmospheric Chemistry Division, National Center for Atmospheric Research (NCAR), PO Box 3000, Boulder, CO 80307 (United States); Langhorne, Nicholas [US Office of Naval Research Global, Edison House, 223 Old Marylebone Road, London (United Kingdom); Nisbet, Euan G [Department of Geology, Royal Holloway, University of London, Egham, Surrey TW20 0EX (United Kingdom); Riedel, Michael [Earth and Planetary Sciences, McGill University, 3450 University Street, Montreal, QC, H3A 2A7 (Canada); Wang Weihua [Computer Network Information Center, Chinese Academy of Sciences, No. 4, 4th South Street, ZhongGuanCun, PO Box 349, Haidian District, Beijing 100080 (China); Yakushev, Vladimir, E-mail: krey@iiasa.ac.a [Gazprom VNIIGAZ LLC, Razvilka, Leninsky District, Moscow Region, 142717 (Russian Federation)

    2009-09-15

    Methane hydrates, ice-like compounds in which methane is held in crystalline cages formed by water molecules, are widespread in areas of permafrost such as the Arctic and in sediments on the continental margins. They are a potentially vast fossil fuel energy source but, at the same time, could be destabilized by changing pressure-temperature conditions due to climate change, potentially leading to strong positive carbon-climate feedbacks. To enhance our understanding of both the vulnerability of and the opportunity provided by methane hydrates, it is necessary (i) to conduct basic research that improves the highly uncertain estimates of hydrate occurrences and their response to changing environmental conditions, and (ii) to integrate the agendas of energy security and climate change which can provide an opportunity for methane hydrates-in particular if combined with carbon capture and storage-to be used as a 'bridge fuel' between carbon-intensive fossil energies and zero-emission energies. Taken one step further, exploitation of dissociating methane hydrates could even mitigate against escape of methane to the atmosphere. Despite these opportunities, so far, methane hydrates have been largely absent from energy and climate discussions, including global hydrocarbon assessments and the Fourth Assessment Report of the Intergovernmental Panel on Climate Change.

  13. Wound healing and hyper-hydration: a counterintuitive model.

    Science.gov (United States)

    Rippon, M G; Ousey, K; Cutting, K F

    2016-02-01

    Winter's seminal work in the 1960s relating to providing an optimal level of moisture to aid wound healing (granulation and re-epithelialisation) has been the single most effective advance in wound care over many decades. As such the development of advanced wound dressings that manage the fluidic wound environment have provided significant benefits in terms of healing to both patient and clinician. Although moist wound healing provides the guiding management principle, confusion may arise between what is deemed to be an adequate level of tissue hydration and the risk of developing maceration. In addition, the counter-intuitive model 'hyper-hydration' of tissue appears to frustrate the moist wound healing approach and advocate a course of intervention whereby tissue is hydrated beyond what is a normally acceptable therapeutic level. This paper discusses tissue hydration, the cause and effect of maceration and distinguishes these from hyper-hydration of tissue. The rationale is to provide the clinician with a knowledge base that allows optimisation of treatment and outcomes and explains the reasoning behind wound healing using hyper-hydration. Declaration of interest: K. Cutting is a Clinical Research Consultant to the medical device and biotechnology industry. M. Rippon is Visiting Clinical Research Fellow, University of Huddersfield and K. Ousey provides consultancy for a range of companies through the University of Huddersfield including consultancy services for Paul Hartmann Ltd on HydroTherapy products.

  14. Hydrate plugging or slurry flow : effect of key variables

    Energy Technology Data Exchange (ETDEWEB)

    Dellecase, E.; Geraci, G.; Barrios, L.; Estanga, D.; Domingues, R.; Volk, M. [Tulsa Univ., Tulsa, OK (United States)

    2008-07-01

    Although oil and gas companies have proven design criteria and proper operating procedures to prevent hydrate plugs from forming, hydrates remain the primary issue in flow assurance. The costs associated with hydrate prevention affect project economics, particularly in deepwater pipelines. As such, there is an interest in developing a technology that allows hydrates to be transported as a slurry, while avoiding plugs. The feasibility of managing such hydrate flow was investigated. This study used a hydrate flow loop to investigate the effects of flow conditions on the transportability of a slurry in both steady-state and restart conditions. For most cases, uninhibited steady-state slurry flow conditions above 25 per cent water-cut were marginal, and most likely not feasible at 50 per cent water-cut or above. Liquid loading and velocity appeared to have a marginal effect on plugging tendency. However, minimum velocity may be needed to guarantee slurry transportation. Some of the important parameters and key variables that determine if a plug will form, particularly in restart conditions, include oil-water dispersion properties; oil-water phase segregation on the plugging tendency of model fluids; the location and state of the water; and the flow pattern. It was concluded that the plugging behaviour of oil systems changes with these variables, and with the oil-water chemistry. As such, specific strategies must be developed for each field. 4 refs., 1 tab., 14 figs.

  15. The search for green inhibitors : perturbing hydrate growth with bugs

    Energy Technology Data Exchange (ETDEWEB)

    Huva, E.; Gordienko, R. [Queen' s Univ., Kingston, ON (Canada). Dept. of Biology; Ripmeester, J.; Zeng, H. [Queen' s Univ., Kingston, ON (Canada). Dept. of Biology]|[National Research Council of Canada, Ottawa, ON (Canada). Steacie Inst. for Molecular Sciences; Walker, V.K. [Queen' s Univ., Kingston, ON (Canada). Dept. of Biology]|[Queen' s Univ., Kingston, ON (Canada). Dept. of Microbiology and Immunology

    2008-07-01

    The ability of some organisms, such as insects and microbes, to survive low temperatures can be attributed to the production of either ice nucleating proteins (INPs) or antifreeze proteins (AFPs). INPs can direct crystal growth by inducing rapid ice formation. AFPs adsorb to ice embryos and decrease the temperature at which the ice grows. Certain AFPs can also inhibit the crystallization of clathrate hydrates and eliminate more rapid recrystallization or memory effect. This paper presented a study that involved the examination of bacterial species with ice-associating properties for their effect on tetrahydrofuran (THF) hydrate crystallization. As part of the study, THF hydrate formation was inhibited in the presence of cultures containing the ice-associating bacterium chryseobacterium C14. The paper discussed the methods used for the study, including hydrate formation and reformation in the presence of ice-associating bacteria and the development of a clathrate hydrate affinity purification technique. A 40 per cent reduction in crystallization was observed, indicating their potential as a commercial green inhibitor for hydrates. In addition, there was no elimination of memory effect, and little supporting evidence was seen for nucleation inhibition by any of the bacteria. 17 refs., 1 tab., 3 figs.

  16. Three-phase flow of submarine gas hydrate pipe transport

    Institute of Scientific and Technical Information of China (English)

    李立; 徐海良; 杨放琼

    2015-01-01

    In the hydraulic transporting process of cutter-suction mining natural gas hydrate, when the temperature−pressure equilibrium of gas hydrate is broken, gas hydrates dissociate into gas. As a result, solid−liquid two-phase flow (hydrate and water) transforms into gas−solid−liquid three-phase flow (methane, hydrate and water) inside the pipeline. The Euler model and CFD-PBM model were used to simulate gas−solid−liquid three-phase flow. Numerical simulation results show that the gas and solid phase gradually accumulate to the center of the pipe. Flow velocity decreases from center to boundary of the pipe along the radial direction. Comparison of numerical simulation results of two models reveals that the flow state simulated by CFD-PBM model is more uniform than that simulated by Euler model, and the main behavior of the bubble is small bubbles coalescence to large one. Comparison of numerical simulation and experimental investigation shows that the values of flow velocity and gas fraction in CFD-PBM model agree with experimental data better than those in Euler model. The proposed PBM model provides a more accurate and effective way to estimate three-phase flow state of transporting gas hydrate within the submarine pipeline.

  17. High-pressure transformations in sulfuric acid hydrates

    International Nuclear Information System (INIS)

    The Galilean moons of Jupiter; Io, Europa, Ganymede and Callisto, have surfaces that are composed of very different materials to the silicates that make up our Earth. For Europa and Ganymede, two moons under intense investigation from past and future space missions, their surfaces are made up of ice and hydrates. Despite the apparent ‘simplicity’ of these materials, we still observe very complex geological formations on these moons – including subduction. This means we need to understand the transformations of candidate surface materials under a range of pressure/temperature conditions in order to accurately explain the formations on these icy surfaces. One hydrate candidate material for the surfaces of these moons are sulfuric acid hydrates, formed from radolytic sulfur (from Io) reacting with the surface ice. Sulfuric acid hydrates have already been established to have a complex phase diagram with composition. We have now used the Mito cell at the PLANET instrument to undertake the first investigation of the high-pressure behavior of the water rich sulfuric acid hydrates. Compressing at 100 K and 180 K we see that the hemitriskaidekahydrate becomes the stable water-rich hydrate and observe some interesting relaxation behaviour in this material at pressure, which could have significant consequences for the interiors of Ganymede.

  18. SCHEMES OF GAS PRODUCTION FROM NATURAL GAS HYDRATES

    Institute of Scientific and Technical Information of China (English)

    李淑霞; 陈月明; 杜庆军

    2003-01-01

    Natural gas hydrates are a kind of nonpolluting and high quality energy resources for future, the reserves of which are about twice of the carbon of the current fossil energy (petroleum, natural gas and coal) on the earth. And it will be the most important energy for the 21st century. The energy balance and numerical simulation are applied to study the schemes of the natural gas hydrates production in this paper,and it is considered that both depressurization and thermal stimulation are effective methods for exploiting natural gas hydrates, and that the gas production of the thermal stimulation is higher than that of the depressurization. But thermal stimulation is non-economic because it requires large amounts of energy.Therefore the combination of the two methods is a preferable method for the current development of the natural gas hydrates. The main factors which influence the production of natural gas hydrates are: the temperature of injected water, the injection rate, the initial saturation of the hydrates and the initial temperature of the reservoir which is the most important factor.

  19. Pectin as an Extraordinary Natural Kinetic Hydrate Inhibitor

    Science.gov (United States)

    Xu, Shurui; Fan, Shuanshi; Fang, Songtian; Lang, Xuemei; Wang, Yanhong; Chen, Jun

    2016-03-01

    Pectin as a novel natural kinetic hydrate inhibitor, expected to be eco-friendly and sufficiently biodegradable, was studied in this paper. The novel crystal growth inhibition (CGI) and standard induction time methods were used to evaluate its effect as hydrate inhibitor. It could successfully inhibit methane hydrate formation at subcooling temperature up to 12.5 °C and dramatically slowed the hydrate crystal growth. The dosage of pectin decreased by 66% and effective time extended 10 times than typical kinetic inhibitor. Besides, its maximum growth rate was no more than 2.0%/h, which was far less than 5.5%/h of growth rate for PVCap at the same dosage. The most prominent feature was that it totally inhibited methane hydrate crystal rapid growth when hydrate crystalline occurred. Moreover, in terms of typical natural inhibitors, the inhibition activity of pectin increased 10.0-fold in induction time and 2.5-fold in subcooling temperature. The extraordinary inhibition activity is closely related to its hydrogen bonding interaction with water molecules and the hydrophilic structure. Finally, the biodegradability and economical efficiency of pectin were also taken into consideration. The results showed the biodegradability improved 75.0% and the cost reduced by more than 73.3% compared to typical commercial kinetic inhibitors.

  20. Towards a fundamental understanding of natural gas hydrates.

    Science.gov (United States)

    Koh, Carolyn A

    2002-05-01

    Gas clathrate hydrates were first identified in 1810 by Sir Humphrey Davy. However, it is believed that other scientists, including Priestley, may have observed their existence before this date. They are solid crystalline inclusion compounds consisting of polyhedral water cavities which enclathrate small gas molecules. Natural gas hydrates are important industrially because the occurrence of these solids in subsea gas pipelines presents high economic loss and ecological risks, as well as potential safety hazards to exploration and transmission personnel. On the other hand, they also have technological importance in separation processes, fuel transportation and storage. They are also a potential fuel resource because natural deposits of predominantly methane hydrate are found in permafrost and continental margins. To progress with understanding and tackling some of the technological challenges relating to natural gas hydrate formation, inhibition and decomposition one needs to develop a fundamental understanding of the molecular mechanisms involved in these processes. This fundamental understanding is also important to the broader field of inclusion chemistry. The present article focuses on the application of a range of physico-chemical techniques and approaches for gaining a fundamental understanding of natural gas hydrate formation, decomposition and inhibition. This article is complementary to other reviews in this field, which have focused more on the applied, engineering and technological aspects of clathrate hydrates. PMID:12122641

  1. Water Intake and Hydration Indices in Healthy European Adults: The European Hydration Research Study (EHRS).

    Science.gov (United States)

    Malisova, Olga; Athanasatou, Adelais; Pepa, Alex; Husemann, Marlien; Domnik, Kirsten; Braun, Hans; Mora-Rodriguez, Ricardo; Ortega, Juan F; Fernandez-Elias, Valentin E; Kapsokefalou, Maria

    2016-01-01

    Hydration status is linked with health, wellness, and performance. We evaluated hydration status, water intake, and urine output for seven consecutive days in healthy adults. Volunteers living in Spain, Germany, or Greece (n = 573, 39 ± 12 years (51.1% males), 25.0 ± 4.6 kg/m² BMI) participated in an eight-day study protocol. Total water intake was estimated from seven-day food and drink diaries. Hydration status was measured in urine samples collected over 24 h for seven days and in blood samples collected in fasting state on the mornings of days 1 and 8. Total daily water intake was 2.75 ± 1.01 L, water from beverages 2.10 ± 0.91 L, water from foods 0.66 ± 0.29 L. Urine parameters were: 24 h volume 1.65 ± 0.70 L, 24 h osmolality 631 ± 221 mOsmol/kg Η₂Ο, 24 h specific gravity 1.017 ± 0.005, 24 h excretion of sodium 166.9 ± 54.7 mEq, 24 h excretion of potassium 72.4 ± 24.6 mEq, color chart 4.2 ± 1.4. Predictors for urine osmolality were age, country, gender, and BMI. Blood indices were: haemoglobin concentration 14.7 ± 1.7 g/dL, hematocrit 43% ± 4% and serum osmolality 294 ± 9 mOsmol/kg Η₂Ο. Daily water intake was higher in summer (2.8 ± 1.02 L) than in winter (2.6 ± 0.98 L) (p = 0.019). Water intake was associated negatively with urine specific gravity, urine color, and urine sodium and potassium concentrations (p < 0.01). Applying urine osmolality cut-offs, approximately 60% of participants were euhydrated and 20% hyperhydrated or dehydrated. Most participants were euhydrated, but a substantial number of people (40%) deviated from a normal hydration level. PMID:27058557

  2. Water Intake and Hydration Indices in Healthy European Adults: The European Hydration Research Study (EHRS

    Directory of Open Access Journals (Sweden)

    Olga Malisova

    2016-04-01

    Full Text Available Hydration status is linked with health, wellness, and performance. We evaluated hydration status, water intake, and urine output for seven consecutive days in healthy adults. Volunteers living in Spain, Germany, or Greece (n = 573, 39 ± 12 years (51.1% males, 25.0 ± 4.6 kg/m2 BMI participated in an eight-day study protocol. Total water intake was estimated from seven-day food and drink diaries. Hydration status was measured in urine samples collected over 24 h for seven days and in blood samples collected in fasting state on the mornings of days 1 and 8. Total daily water intake was 2.75 ± 1.01 L, water from beverages 2.10 ± 0.91 L, water from foods 0.66 ± 0.29 L. Urine parameters were: 24 h volume 1.65 ± 0.70 L, 24 h osmolality 631 ± 221 mOsmol/kg Η2Ο, 24 h specific gravity 1.017 ± 0.005, 24 h excretion of sodium 166.9 ± 54.7 mEq, 24 h excretion of potassium 72.4 ± 24.6 mEq, color chart 4.2 ± 1.4. Predictors for urine osmolality were age, country, gender, and BMI. Blood indices were: haemoglobin concentration 14.7 ± 1.7 g/dL, hematocrit 43% ± 4% and serum osmolality 294 ± 9 mOsmol/kg Η2Ο. Daily water intake was higher in summer (2.8 ± 1.02 L than in winter (2.6 ± 0.98 L (p = 0.019. Water intake was associated negatively with urine specific gravity, urine color, and urine sodium and potassium concentrations (p < 0.01. Applying urine osmolality cut-offs, approximately 60% of participants were euhydrated and 20% hyperhydrated or dehydrated. Most participants were euhydrated, but a substantial number of people (40% deviated from a normal hydration level.

  3. Dissolution Rates of Synthetic Methane Hydrate and Carbon Dioxide Hydrate in Undersaturated Seawater at 1000m depth

    Science.gov (United States)

    Rehder, G.; Kirby, S. H.; Durham, W. B.; Brewer, P. G.; Stern, L.; Peltzer, E. T.; Pinkston, J.

    2001-12-01

    Dissolution of synthetic methane and carbon dioxide hydrates was monitored after their transport to the ocean floor at 1000m depth. Cylindrical test specimens were initially grown in the laboratory by combining either cold, pressurized methane gas or pressurized liquid CO2 with sieved granular water ice, then heating the reactants through the H2O melting point. Samples were then hydrostatically compacted to near-zero porosity, with resulting geometry of approximately 2.5 cm in diameter by 3-4 cm in length. Two samples each of methane and carbon dioxide hydrate were placed in a custom-made sample display rack having individual compartments for each sample with a transparent polycarbonate front window, and side and back walls of a flexible fine-mesh screen that permitted seawater flow around the hydrates. The sample rack was then transferred to the ocean in a stainless steel transport vessel pressurized with 10 MPa methane using the (ROV) Ventana. On the seafloor, the sample display rack was removed from the pressure vessel and secured in a stand attached to an autonomous underwater video recorder system using a time-programmable Hi8 video recorder. The samples were continuously monitored for 2.30 h using VentanaIs HDTV camera system, then followed by 20.75 h observation with the autonomous Hi8 time-lapse camera system (15 s every 0.25 h), and additional 3.33 h HDTV observation at the end of the experiment. Loss of volume and dissolution rates of the hydrates were derived from the measurement of the change of the projected diameter of the individual samples over time. During the first 2.30 h, the diameter of the two CO2 hydrates decreased from 22 mm to 15 and 13 mm, respectively. Diameter loss followed a generally linear trend of 0.94 and 1.20 μ m/sec, corresponding to a dissolution rate of 13 to 17 mole CO2/m2h. Similar short-term oscillations about this linear trend were observed on both samples, suggesting a link to bottom current velocity. The CH4 hydrates

  4. DNA hydration studied by neutron fiber diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Fuller, W.; Forsyth, V.T.; Mahendrasingam, A.; Langan, P.; Pigram, W.J. [Keele Univ. (United Kingdom)] [and others

    1994-12-31

    The development of neutron high angle fiber diffraction to investigate the location of water around the deoxyribonucleic acid (DNA) double-helix is described. The power of the technique is illustrated by its application to the D and A conformations of DNA using the single crystal diffractometer, D19, at the Institute Laue-Langevin, Grenoble and the time of flight diffractometer, SXD, at the Rutherford Appleton ISIS Spallation Neutron Source. These studies show the existence of bound water closely associated with the DNA. The patterns of hydration in these two DNA conformations are quite distinct and are compared to those observed in X-ray single crystal studies of two-stranded oligodeoxynucleotides. Information on the location of water around the DNA double-helix from the neutron fiber diffraction studies is combined with that on the location of alkali metal cations from complementary X-ray high angle fiber diffraction studies at the Daresbury Laboratory SRS using synchrotron radiation. These analyses emphasize the importance of viewing DNA, water and ions as a single system with specific interactions between the three components and provide a basis for understanding the effect of changes in the concentration of water and ions in inducing conformations] transitions in the DNA double-helix.

  5. On the free energy of ionic hydration

    CERN Document Server

    Hummer, G; García, A E; Hummer, Gerhard; Pratt, Lawrence R.; Garcia, Angel E.

    1995-01-01

    The hydration free energies of ions exhibit an approximately quadratic dependence on the ionic charge, as predicted by the Born model. We analyze this behavior using second-order perturbation theory. This provides effective methods to calculating free energies from equilibrium computer simulations. The average and the fluctuation of the electrostatic potential at charge sites appear as the first coefficients in a Taylor expansion of the free energy of charging. Combining the data from different charge states allows calculation of free-energy profiles as a function of the ionic charge. The first two Taylor coefficients of the free-energy profiles can be computed accurately from equi- librium simulations; but they are affected by a strong system-size dependence. We apply corrections for these finite-size effects by using Ewald lattice sum- mation and adding the self-interactions consistently. Results are presented for a model ion with methane-like Lennard-Jones parameters in SPC water. We find two very closely ...

  6. Formation and Dissociation of Methane Hydrates from Seawater in Consolidated Sand: Mimicking Methane Hydrate Dynamics beneath the Seafloor

    Directory of Open Access Journals (Sweden)

    Prasad B. Kerkar

    2013-11-01

    Full Text Available Methane hydrate formation and dissociation kinetics were investigated in seawater-saturated consolidated Ottawa sand-pack under sub-seafloor conditions to study the influence of effective pressure on formation and dissociation kinetics. To simulate a sub-seafloor environment, the pore-pressure was varied relative to confining pressure in successive experiments. Hydrate formation was achieved by methane charging followed by sediment cooling. The formation of hydrates was delayed with increasing degree of consolidation. Hydrate dissociation by step-wise depressurization was instantaneous, emanating preferentially from the interior of the sand-pack. Pressure drops during dissociation and in situ temperature controlled the degree of endothermic cooling within sediments. In a closed system, the post-depressurization dissociation was succeeded by thermally induced dissociation and pressure-temperature conditions followed theoretical methane-seawater equilibrium conditions and exhibited excess pore pressure governed by the pore diameter. These post-depressurization equilibrium values for the methane hydrates in seawater saturated consolidated sand-pack were used to estimate the enthalpy of dissociation of 55.83 ± 1.41 kJ/mol. These values were found to be lower than those reported in earlier literature for bulk hydrates from seawater (58.84 kJ/mol and pure water (62.61 kJ/mol due to excess pore pressure generated within confined sediment system under investigation. However, these observations could be significant in the case of hydrate dissociation in a subseafloor environment where dissociation due to depressurization could result in an instantaneous methane release followed by slow thermally induced dissociation. The excess pore pressure generated during hydrate dissociation could be higher within fine-grained sediments with faults and barriers present in subseafloor settings which could cause shifting in geological layers.

  7. Study on molecular controlled mining system of methane hydrate; Methane hydrate no bunshi seigyo mining ni kansuru kenkyu

    Energy Technology Data Exchange (ETDEWEB)

    Kuriyagawa, M.; Saito, T.; Kobayashi, H.; Karasawa, H.; Kiyono , F.; Nagaoki, R.; Yamamoto, Y.; Komai, T.; Haneda, H.; Takahashi, Y. [National Institute for Resources and Environment, Tsukuba (Japan); Nada, H. [Science and Technology Agency, Tokyo (Japan)

    1997-02-01

    Basic studies are conducted for the collection of methane from the methane hydrate that exists at levels deeper than 500m in the sea. The relationship between the hydrate generation mechanism and water cluster structure is examined by use of mass spectronomy. It is found that, among the stable liquid phase clusters, the (H2O)21H{sup +} cluster is the most stable. Stable hydrate clusters are in presence in quantities, and participate in the formation of hydrate crystal nuclei. For the elucidation of the nucleus formation mechanism, a kinetic simulation is conducted of molecules in the cohesion system consisting of water and methane molecules. Water molecules that array near methane molecules at the normal pressure is disarrayed under a higher pressure for rearray into a hydrate structure. Hydrate formation and breakdown in the three-phase equilibrium state of H2O, CH4, and CO2 at a low temperature and high pressure are tested, which discloses that supercooling is required for formation, that it is possible to extract CH4 first for replacement by guest molecule CO2 since CO2 is stabler than CH4 at a lower pressure or higher temperature, and that formation is easier to take place when the grain diameter is larger at the formation point since larger grain diameters result in a higher formation temperature. 3 figs.

  8. Hydrate Evolution in Response to Ongoing Environmental Shifts

    Energy Technology Data Exchange (ETDEWEB)

    Rempel, Alan [Univ. of Oregon, Eugene, OR (United States)

    2015-12-31

    Natural gas hydrates have the potential to become a vital domestic clean-burning energy source. However, past changes in environmental conditions have caused hydrates to become unstable and trigger both massive submarine landslides and the development of crater-like pockmarks, thereby releasing methane into the overlying seawater and atmosphere, where it acts as a powerful greenhouse gas. This project was designed to fill critical gaps in our understanding of domestic hydrate resources and improve forecasts for their response to environmental shifts. Project work can be separated into three interrelated components, each involving the development of predictive mathematical models. The first project component concerns the role of sediment properties on the development and dissociation of concentrated hydrate anomalies. To this end, we developed numerical models to predict equilibrium solubility of methane in twophase equilibrium with hydrate as a function of measureable porous medium characteristics. The second project component concerned the evolution of hydrate distribution in heterogeneous reservoirs. To this end, we developed numerical models to predict the growth and decay of anomalies in representative physical environments. The third project component concerned the stability of hydrate-bearing slopes under changing environmental conditions. To this end, we developed numerical treatments of pore pressure evolution and consolidation, then used "infinite-slope" analysis to approximate the landslide potential in representative physical environments, and developed a "rate-and-state" frictional formulation to assess the stability of finite slip patches that are hypothesized to develop in response to the dissociation of hydrate anomalies. The increased predictive capabilities that result from this work provide a framework for interpreting field observations of hydrate anomalies in terms of the history of environmental forcing that led to their development. Moreover

  9. Cryopegs as destabilization factor of intra-permafrost gas hydrates

    Science.gov (United States)

    Chuvilin, Evgeny; Bukhanov, Boris; Istomin, Vladimir

    2016-04-01

    A characteristic feature of permafrost soils in the Arctic is widespread intra-permafrost unfrozen brine lenses - cryopegs. They are often found in permafrost horizons in the north part of Western Siberia, in particular, on the Yamal Peninsula. Cryopegs depths in permafrost zone can be tens and hundreds of meters from the top of frozen strata. The chemical composition of natural cryopegs is close to sea waters, but is characterized by high mineralization. They have a sodium-chloride primary composition with a minor amount of sulphate. Mineralization of cryopegs brine is often hundreds of grams per liter, and the temperature is around -6…-8 °C. The formation of cryopegs in permafrost is associated with processes of long-term freezing of sediments and cryogenic concentration of salts and salt solutions in local areas. The cryopegs' formation can take place in the course of permafrost evolution at the sea transgressions and regressions during freezing of saline sea sediments. Very important feature of cryopegs in permafrost is their transformation in the process of changing temperature and pressure conditions. As a result, the salinity and chemical composition are changed and in addition the cryopegs' location can be changed during their migration. The cryopegs migration violates the thermodynamic conditions of existence intra-permafrost gas hydrate formations, especially the relic gas hydrates deposits, which are situated in the shallow permafrost up to 100 meters depth in a metastable state [1]. The interaction cryopegs with gas hydrates accumulations can cause decomposition of intra-permafrost hydrates. Moreover, the increasing of salt and unfrozen water content in sedimentary rocks sharply reduce the efficiency of gas hydrates self-preservation in frozen soils. It is confirmed by experimental investigations of interaction of frozen gas hydrate bearing sediments with salt solutions [2]. So, horizons with elevated pressure can appear, as a result of gas hydrate

  10. Absolute Hydration Free Energies of Ions, Ion-Water Clusters, and Quasi-chemical Theory

    CERN Document Server

    Asthagiri, D; Ashbaugh, H S; Pratt, Lawrence R.

    2003-01-01

    Experimental studies on ion-water clusters have provided insights into the microscopic aspects of hydration phenomena. One common view is that extending those experimental studies to larger cluster sizes would give the single ion absolute hydration free energies not obtainable by classical thermodynamic methods. This issue is reanalyzed in the context of recent computations and molecular theories on ion hydration, particularly considering the hydration of H$^+$, Li$^+$, Na$^+$, and HO$^-$ ions and thence the hydration of neutral ion pairs. The hydration free energies of neutral pairs computed here are in good agreement with experimental results, whereas the calculated absolute hydration free energies, and the excess chemical potentials, deviate consistently from some recently tabulated hydration free energies based on ion-water cluster data. We show how the single ion absolute hydration free energies are not separated from the potential of the phase in recent analyses of ion-water cluster data, even in the li...

  11. Effect of under-inhibition with methanol and ethylene glycol on the hydrate control process

    Energy Technology Data Exchange (ETDEWEB)

    Yousif, M.H.

    1996-12-31

    Hydrate control can be achieved by chemical injection. Currently, methanol and ethylene glycol are the most widely used inhibitors in offshore hydrate control operations. To achieve effective hydrate inhibition, a sufficient amount of inhibitor must be injected to shift the thermodynamic equilibrium condition for hydrate formation outside the pipeline operating pressure and temperature. Recently published field experiments showed that hydrate blockages form more readily in under-inhibited systems than in systems completely without inhibitor. A laboratory study is conducted to determine the effect of low concentration (1--5wt%) methanol and ethylene glycol on the hydrate formation process. The results show that, although these chemicals are effective hydrate inhibitors when added in sufficient quantities, they actually enhance the rate of hydrate formation when added at low concentrations to the water. Furthermore, the presence of these chemicals seems to affect the size of the forming hydrate particles.

  12. The specific surface area of methane hydrate formed in different conditions and manners

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The specific surface area of methane hydrates, formed both in the presence and absence of sodium dodecyl sulfate (SDS) and processed in different manners (stirring, compacting, holding the hydrates at the formation conditions for different periods of time, cooling the hydrates for different periods of time before depressurizing them), was measured under atmospheric pressure and temperatures below ice point. It was found that the specific surface area of hydrate increased with the decreasing temperature. The methane hydrate in the presence of SDS was shown to be of bigger specific surface areas than pure methane hydrates. The experimental results further demonstrated that the manners of forming and processing hydrates affected the specific surface area of hydrate samples. Stirring or compacting made the hydrate become finer and led to a bigger specific surface area.

  13. Microstructural characteristics of natural gas hydrates hosted in various sand sediments.

    Science.gov (United States)

    Zhao, Jiafei; Yang, Lei; Liu, Yu; Song, Yongchen

    2015-09-21

    Natural gas hydrates have aroused worldwide interest due to their energy potential and possible impact on climate. The occurrence of natural gas hydrates hosted in the pores of sediments governs the seismic exploration, resource assessment, stability of deposits, and gas production from natural gas hydrate reserves. In order to investigate the microstructure of natural gas hydrates occurring in pores, natural gas hydrate-bearing sediments were visualized using microfocus X-ray computed tomography (CT). Various types of sands with different grain sizes and wettability were used to study the effect of porous materials on the occurrence of natural gas hydrates. Spatial distributions of methane gas, natural gas hydrates, water, and sands were directly identified. This work indicates that natural gas hydrates tend to reside mainly within pore spaces and do not come in contact with adjacent sands. Such an occurring model of natural gas hydrates is termed the floating model. Furthermore, natural gas hydrates were observed to nucleate at gas-water interfaces as lens-shaped clusters. Smaller sand grain sizes contribute to higher hydrate saturation. The wetting behavior of various sands had little effect on the occurrence of natural gas hydrates within pores. Additionally, geometric properties of the sediments were collected through CT image reconstructions. These findings will be instructive for understanding the microstructure of natural gas hydrates within major global reserves and for future resource utilization of natural gas hydrates. PMID:26277891

  14. Hydrate phase equilibrium and structure for (methane + ethane + tetrahydrofuran + water) system

    International Nuclear Information System (INIS)

    The separation of methane and ethane through forming hydrate is a possible choice in natural gas, oil processing, or ethylene producing. The hydrate formation conditions of five groups of (methane + ethane) binary gas mixtures in the presence of 0.06 mole fraction tetrahydrofuran (THF) in water were obtained at temperatures ranging from (277.7 to 288.2) K. In most cases, the presence of THF in water can lower the hydrate formation pressure of (methane + ethane) remarkably. However, when the composition of ethane is as high as 0.832, it is more difficult to form hydrate than without THF system. Phase equilibrium model for hydrates containing THF was developed based on a two-step hydrate formation mechanism. The structure of hydrates formed from (methane + ethane + THF + water) system was also determined by Raman spectroscopy. When THF concentration in initial aqueous solution was only 0.06 mole fraction, the coexistence of structure I hydrate dominated by ethane and structure II hydrate dominated by THF in the hydrate sample was clearly demonstrated by Raman spectroscopic data. On the contrary, only structure II hydrate existed in the hydrate sample formed from (methane + ethane + THF + water) system when THF concentration in initial aqueous solution was increased to 0.10 mole fraction. It indicated that higher THF concentration inhibited the formation of structure I hydrate dominated by ethane and therefore lowered the trapping of ethane in hydrate. It implies a very promising method to increase the separation efficiency of methane and ethane.

  15. Gas hydrate dissociation in sediments: Pressure-temperature evolution

    Science.gov (United States)

    Kwon, Tae-Hyuk; Cho, Gye-Chun; Santamarina, J. Carlos

    2008-03-01

    Hydrate-bearing sediments may destabilize spontaneously as part of geological processes, unavoidably during petroleum drilling/production operations or intentionally as part of gas extraction from the hydrate itself. In all cases, high pore fluid pressure generation is anticipated during hydrate dissociation. A comprehensive formulation is derived for the prediction of fluid pressure evolution in hydrate-bearing sediments subjected to thermal stimulation without mass transfer. The formulation considers pressure- and temperature-dependent volume changes in all phases, effective stress-controlled sediment compressibility, capillarity, and the relative solubilities of fluids. Salient implications are explored through parametric studies. The model properly reproduces experimental data, including the PT evolution along the phase boundary during dissociation and the effect of capillarity. Pore fluid pressure generation is proportional to the initial hydrate fraction and the sediment bulk stiffness; is inversely proportional to the initial gas fraction and gas solubility; and is limited by changes in effective stress that cause the failure of the sediment. When the sediment stiffness is high, the generated pore pressure reflects thermal and pressure changes in water, hydrate, and mineral densities. Comparative analyses for CO2 and CH4 highlight the role of gas solubility in excess pore fluid pressure generation. Dissociation in small pores experiences melting point depression due to changes in water activity, and lower pore fluid pressure generation due to the higher gas pressure in small gas bubbles. Capillarity effects may be disregarded in silts and sands, when hydrates are present in nodules and lenses and when the sediment experiences hydraulic fracture.

  16. Mechanisms of deep slab hydration: numerical modeling and implications

    Science.gov (United States)

    Faccenda, M.; Gerya, T.; Burlini, L.

    2009-12-01

    Water is a fundamental component of the Earth, affecting its internal structures and dynamics. Sea-water enters the subduction factory via slab hydration that occurs mainly at the trench and is subsequently released in the upper mantle wedge because of slab warming and de-hydration. In the last decades, the scientific research has focused mainly on geophysical processes related to the de-hydration of the slab. However, not much is known on how and to which extent the subducting oceanic plate get hydrated. In order to investigate hydration of the slab, we performed 2D numerical models of a spontaneously bending oceanic plate using I2ELVIS code that account for visco-elasto-plastic rheologies and where fluid flow is regulated by Darci’s law. At the outer rise, bending-related slab faulting occurs, providing a pathway for water percolation in the slab. Faults generally deep trenchward, but antithetic faults are also common. Downward deep fluid flow establishes during brittle extensional deformation at the trench outer rise producing strong variation of the tectonic pressure and causing sub-hydrostatic or even negative pressure gradients along bending related normal faults through which fluids are pumped. The results of the numerical experiment indicate that water can be transported down and stored in the bending area via serpentinization of the normal faults. Deep slab hydration has important implications for the rheological structure, seismicity and seismic anisotropy of the upper mantle because: 1) more water can be stored in the slab producing more enhanced weakening of the mantle wedge, 2) intermediate and deep intra-slab earthquakes can be triggered by slab de-hydration, 3) DHMS phases, able to bring fluids down to the transition zone and lower mantle, could form in the cold core of the slab, 4) the slab could acquire a strong anisotropic fabric responsible for the anisotropic patterns observed at subduction zones.

  17. Hydration Properties of Soybean Protein Isolates

    Directory of Open Access Journals (Sweden)

    G. Remondetto

    2001-12-01

    Full Text Available Hydration properties of soybean isolates with different processing conditions (heat treatments, pH and protein concentrations were studied. Degree of denaturation,, solubility in water, in 0.2mol/L NaCl, and in media of different sodium dodecyl sulfate concentrations, viscosity and water imbibing capacity of the different samples were determinated and correlated. Treatments at temperatures higher than 80ºC denatured 11S and 7S proteins, leading to exposure of hydrophobic groups, which produced insoluble aggregates either in water or in high ionic strength media. These isolates possessed high water imbibing capacities and gave rise to viscous dispersions. Significant correlations were obtained between hydration properties and the "m" coefficient as calculated by a power law equation relating viscosity with the protein concentration of the dispersion. This "m" coefficient also correlated with the denaturation enthalpy of the protein isolates. On the basis of these results, it might be suggested that the "m" coefficient - dependent of the hydrodynamic behaviour of the particles - was a good estimator of the degree of protein denaturation.Estudaram-se as propriedades de hidratação de isolados de soja com diferentes condições de procesamento (tratamentos térmicos, pH e concentração de proteínas. Para diferentes amostras determinaram-se e correlacionaram-se o gráu de desnaturalização, a solubilidade em água, em 0,2mol/L NaCl e em diferentes concentrações de dodecil sulfato de sódio, viscosidade e capacidade de absorção de água. Os tratamentos a temperaturas superiores aos 80ºC desnaturaram as fracções 11S e 7S, provocando a exposição de grupos hidrofóbicos os que produziram agregados insolúveis, em água como em solução com alta força iónica. Estes isolados posuiam alta capacidade de absorção de água e dispersões com alta viscosidade. Achou-se uma correlação significativa entre as propriedades de hidratação e o

  18. Role of taurine accumulation in keratinocyte hydration.

    Science.gov (United States)

    Janeke, Guido; Siefken, Wilfried; Carstensen, Stefanie; Springmann, Gunja; Bleck, Oliver; Steinhart, Hans; Höger, Peter; Wittern, Klaus-Peter; Wenck, Horst; Stäb, Franz; Sauermann, Gerhard; Schreiner, Volker; Doering, Thomas

    2003-08-01

    Epidermal keratinocytes are exposed to a low water concentration at the stratum corneum-stratum granulosum interface. When epithelial tissues are osmotically perturbed, cellular protection and cell volume regulation is mediated by accumulation of organic osmolytes such as taurine. Previous studies reported the presence of taurine in the epidermis of several animal species. Therefore, we analyzed human skin for the presence of the taurine transporter (TAUT) and studied the accumulation of taurine as one potential mechanism protecting epidermal keratinocytes from dehydration. According to our results, TAUT is expressed as a 69 kDa protein in human epidermis but not in the dermis. For the epidermis a gradient was evident with maximal levels of TAUT in the outermost granular keratinocyte layer and lower levels in the stratum spinosum. No TAUT was found in the basal layer or in the stratum corneum. Keratinocyte accumulation of taurine was induced by experimental induction of skin dryness via application of silica gel to human skin. Cultured human keratinocytes accumulated taurine in a concentration- and osmolarity-dependent manner. TAUT mRNA levels were increased after exposure of human keratinocytes to hyperosmotic culture medium, indicating osmosensitive TAUT mRNA expression as part of the adaptation of keratinocytes to hyperosmotic stress. Keratinocyte uptake of taurine was inhibited by beta-alanine but not by other osmolytes such as betaine, inositol, or sorbitol. Accumulation of taurine protected cultured human keratinocytes from both osmotically induced and ultraviolet-induced apoptosis. Our data indicate that taurine is an important epidermal osmolyte required to maintain keratinocyte hydration in a dry environment. PMID:12880428

  19. Hydration Status of Adult Population of Yazd

    Directory of Open Access Journals (Sweden)

    MH Lotfi

    2008-07-01

    Full Text Available Introduction: Water is an essential nutrient for life. It comprises 75% of total body weight in infants,60% in adult males and 50% in adult females. Decrease in body water is commonly known as dehydration. Acute or chronic dehydration is a common condition in some population groups, especialy the elderly and those who participate in physical activity in warm enviroments. Potential consequences of dehydration include constipation,urinary tract and respiratory infection,urinary stone disease and there might also be an association between a low habitual fluid intake and some carcinomas,cardiovascular disease and diabetes. Many indices have been investigated to establish their role as markers of dehydration status. Body mass changes,blood indices,urine indices and bioelectrical impedance analysis have been used most widely, but current evidence and opinion tend to favour urine indices as the most convenient and sensitive methods. Methods: This cross sectional study was done for estimating the prevalence of dehydration in adult population(students,nurses,officials,workersin Yazd. These persons were selected randomly. Urine samples of two hundred and thirty persons were obtained at 10-12 AM,and urine specific gravity measured by refractometer (all of the samplesand dip stick (some samples. Finding: According to this study,96.7% of our population had some degree of dehydration.69.7% of them were significantly dehydrated(urine SG>1020 and 4.8% of them were severely dehydrated (urine SG>1030 and the mean specific gravity was 1021±5/65. This study evaluated other factors that could probably indicate hydration status like urine colour, type of drink,frequency of urination and frequency of thirst per day. Conclusion: High percentage of our population were dehydrated which was not correlated to the type of drink but was correlated to urine colour, frequency of urination and frequency of thirst. So, regular monitoring of urine to keep if clear or light

  20. Hydration water and peptide dynamics - two sides of a coin. A neutron scattering and adiabatic calorimetry study at low hydration and cryogenic temperatures

    OpenAIRE

    Margarida Bastos; Nuno Alves; Silvia Maia; Paula Gomes; Akira Inaba; Yuji Miyazaki; Jean Marc Zanotti

    2013-01-01

    In the present work we bridge neutron scattering and calorimetry in the study of a low-hydration sample of a 15-residue hybrid peptide from cecropin and mellitin CA(1-7)M(2-9) of proven antimicrobial activity. Quasielastic and low-frequency inelastic neutron spectra were measured at defined hydration levels a nominally dry sample (specific residual hydration h = 0.060 g/g), a H2O-hydrated (h = 0.49) and a D2O-hydrated one (h = 0.51). Averaged mean square proton mobilities were derived over a ...

  1. Tectonic Controls on Gas Hydrate Distribution off SW Taiwan

    Science.gov (United States)

    Berndt, C.; Chi, W. C.; Jegen, M. D.; Muff, S.; Hölz, S.; Lebas, E.; Sommer, M.; Lin, S.; Liu, C. S.; Lin, A. T.; Klaucke, I.; Klaeschen, D.; Chen, L.; Kunath, P.; McIntosh, K. D.; Feseker, T.

    2015-12-01

    The northern part of the South China Sea is characterized by wide-spread occurrence of bottom simulating reflectors (BSR), indicating the presence of marine gas hydrates. Because the area covers both the tectonically inactive passive margin and the northern termination of the Manila Trench subduction zone while sediment input is broadly similar, this area provides an excellent opportunity to study the influence of tectonic processes on the dynamics of gas hydrate systems. Long-offset multi-channel seismic data show that movement along thrust faults and blind thrust faults caused anticlinal ridges on the active margin, while faults are absent on the passive margin. This coincides with high-hydrate saturations derived from ocean bottom seismometer data and controlled source electromagnetic data, and conspicuous high-amplitude reflections in P-Cable 3D seismic data above the BSR in the anticlinal ridges of the active margin. On the contrary, all geophysical evidence for the passive margin points to normal- to low-hydrate saturations. Geochemical analysis of gas samples collected at seep sites on the active margin show methane with heavy δ13C isotope composition, while gas collected on the passive margin shows highly depleted (light) carbon isotope composition. Thus, we interpret the passive margin as a typical gas hydrate province fuelled by biogenic production of methane and the active margin gas hydrate system as a system that is fuelled not only by biogenic gas production but also by additional advection of thermogenic methane from the subduction system. The location of the highest gas hydrate saturations in the hanging wall next to the thrust faults suggests that the thrust faults represent pathways for the migration of methane. Our findings suggest that the most promising gas hydrate occurrences for exploitation of gas hydrate as an energy source may be found in the core of the active margin roll over anticlines immediately above the BSR and that high

  2. Behavior of calcium silicate hydrate in aluminate solution

    Institute of Scientific and Technical Information of China (English)

    LI Xiao-bin; ZHAO Zhuo; LIU Gui-hua; ZHOU Qiu-sheng; PENG Zhi-hong

    2005-01-01

    Using calcium hydroxide and sodium silicate as starting materials, two kinds of calcium silicate hydrates, CaO · SiO2 · H2O and 2CaO · SiO2 · 1.17H2O, were hydro-thermally synthesized at 120 ℃. The reaction rule of calcium silicate hydrate in aluminate solution was investigated. The result shows that CaO · SiO2 · H2O is more stable than 2CaO · SiO2 · 1.17H2 O in aluminate solution and its stability increases with the increase of reaction temperature but decreases with the increase of caustic concentration. The reaction between calcium silicate hydrate and aluminate solution is mainly through two routes. In the first case, Al replaces partial Si in calcium silicate hydrate, meanwhile 3CaO · Al2 O3 · xSiO2 · (6-2x) H2 O (hydro-garnet) is formed and some SiO2 enters the solution. In the second case, calcium silicate hydrate can react directly with aluminate solution, forming hydro-garnet and Na2O · Al2O3 · 2SiO2 · nH2O (DSP). The desilication reaction of aluminate solution containing silicate could contribute partially to forming DSP.

  3. State of hydration and electrical conductance of ichthyotic skin

    Directory of Open Access Journals (Sweden)

    Gupta A

    1990-01-01

    Full Text Available Dry skin of twelve subjects suffering from ichthyosis vulgaris and the efficacy of a moisturiser-Cotaryl were quantitatively assessed by measuring the skin surface hydration and high frequency (3.5 MHz electrical conductance of skin. The state of hydration and conductance of ichthyotic skin were 86.9 + 24.6 and 11.0 + 5.7 micro-mho respectively, being much less-compared to 132. 0 + 5.3 and 72.5 + 54.0 micro-mho ofnormal subjects. The moisturiser increased the state of hydration and also the electrical conductance of the stratum corneuni to near-normal values and maintained them as long as the application continued. However, both the hydration and the conductance fell sharply within a week of withrawal of the moisturiser. A moisturiser was thus undoubtedly efficacious in ichthyotic skin, but the effect was only temporary. The state of hydration was found, at all stages, to bear a strong positive correlation (r = 0.69 to 0.80 with the skin conductance.

  4. Integrating Natural Gas Hydrates in the Global Carbon Cycle

    Energy Technology Data Exchange (ETDEWEB)

    David Archer; Bruce Buffett

    2011-12-31

    We produced a two-dimensional geological time- and basin-scale model of the sedimentary margin in passive and active settings, for the simulation of the deep sedimentary methane cycle including hydrate formation. Simulation of geochemical data required development of parameterizations for bubble transport in the sediment column, and for the impact of the heterogeneity in the sediment pore fluid flow field, which represent new directions in modeling methane hydrates. The model is somewhat less sensitive to changes in ocean temperature than our previous 1-D model, due to the different methane transport mechanisms in the two codes (pore fluid flow vs. bubble migration). The model is very sensitive to reasonable changes in organic carbon deposition through geologic time, and to details of how the bubbles migrate, in particular how efficiently they are trapped as they rise through undersaturated or oxidizing chemical conditions and the hydrate stability zone. The active margin configuration reproduces the elevated hydrate saturations observed in accretionary wedges such as the Cascadia Margin, but predicts a decrease in the methane inventory per meter of coastline relative to a comparable passive margin case, and a decrease in the hydrate inventory with an increase in the plate subduction rate.

  5. Gas Hydrate Research Database and Web Dissemination Channel

    Energy Technology Data Exchange (ETDEWEB)

    Micheal Frenkel; Kenneth Kroenlein; V Diky; R.D. Chirico; A. Kazakow; C.D. Muzny; M. Frenkel

    2009-09-30

    To facilitate advances in application of technologies pertaining to gas hydrates, a United States database containing experimentally-derived information about those materials was developed. The Clathrate Hydrate Physical Property Database (NIST Standard Reference Database {number_sign} 156) was developed by the TRC Group at NIST in Boulder, Colorado paralleling a highly-successful database of thermodynamic properties of molecular pure compounds and their mixtures and in association with an international effort on the part of CODATA to aid in international data sharing. Development and population of this database relied on the development of three components of information-processing infrastructure: (1) guided data capture (GDC) software designed to convert data and metadata into a well-organized, electronic format, (2) a relational data storage facility to accommodate all types of numerical and metadata within the scope of the project, and (3) a gas hydrate markup language (GHML) developed to standardize data communications between 'data producers' and 'data users'. Having developed the appropriate data storage and communication technologies, a web-based interface for both the new Clathrate Hydrate Physical Property Database, as well as Scientific Results from the Mallik 2002 Gas Hydrate Production Research Well Program was developed and deployed at http://gashydrates.nist.gov.

  6. Stability Analysis of Methane Hydrate-Bearing Soils Considering Dissociation

    Directory of Open Access Journals (Sweden)

    Hiromasa Iwai

    2015-06-01

    Full Text Available It is well known that the methane hydrate dissociation process may lead to unstable behavior such as large ground deformations, uncontrollable gas production, etc. A linear instability analysis was performed in order to investigate which variables have a significant effect on the onset of the instability behavior of methane hydrate-bearing soils subjected to dissociation. In the analysis a simplified viscoplastic constitutive equation is used for the soil sediment. The stability analysis shows that the onset of instability of the material system mainly depends on the strain hardening-softening parameter, the degree of strain, and the permeability for water and gas. Then, we conducted a numerical analysis of gas hydrate-bearing soil considering hydrate dissociation in order to investigate the effect of the parameters on the system. The simulation method used in the present study can describe the chemo-thermo-mechanically coupled behaviors such as phase changes from hydrates to water and gas, temperature changes and ground deformation. From the numerical results, we found that basically the larger the permeability for water and gas is, the more stable the simulation results are. These results are consistent with those obtained from the linear stability analysis.

  7. Transformation of deep-water methane bubbles into hydrate

    CERN Document Server

    Egorov, Alexander V; Rozhkov, Aleksey N

    2013-01-01

    The paper is dedicated to the mechanics of the methane bubbles in the gas hydrate stability zone of the basin. Transformation of deep-water methane bubbles into solid hydrate was investigated in Lake Baikal in situ. Released from the bottom methane bubbles were caught by different traps with transparent walls. It was observed that when bubbles entered into internal space of the trap, the bubbles could be transformed into two different solid hydrate structures depending on ambient conditions. The first structure is hydrate granular matter consisted of solid fragments with sizes of order of 1 mm. The second structure is high porous solid foam consisted of solid bubbles with sizes of order of 5 mm. The formed granular matter did not change during trap lifting up to top border of gas hydrate stability zone, whereas free methane intensively released from solid foam sample during it lifting. It was concluded that the decrease of the depth of bubble sampling and the decrease of the bubble flux rate assist to formati...

  8. Acoustical method of whole-body hydration status monitoring

    Science.gov (United States)

    Sarvazyan, A. P.; Tsyuryupa, S. N.; Calhoun, M.; Utter, A.

    2016-07-01

    An acoustical handheld hydration monitor (HM) for assessing the water balance of the human body was developed. Dehydration is a critical public health problem. Many elderly over age of 65 are particularly vulnerable as are infants and young children. Given that dehydration is both preventable and reversible, the need for an easy-to-perform method for the detection of water imbalance is of the utmost clinical importance. The HM is based on an experimental fact that ultrasound velocity in muscle is a linear function of water content and can be referenced to the hydration status of the body. Studies on the validity of HM for the assessment of whole-body hydration status were conducted in the Appalachian State University, USA, on healthy young adults and on elderly subjects residing at an assisted living facility. The HM was able to track changes in total body water during periods of acute dehydration and rehydration in athletes and day-to-day and diurnal variability of hydration in elderly. Results of human studies indicate that HM has a potential to become an efficient tool for detecting abnormal changes in the body hydration status.

  9. Structural stability of methane hydrate at high pressures

    Science.gov (United States)

    Shu, J.; Chen, X.; Chou, I.-Ming; Yang, W.; Hu, Jiawen; Hemley, R.J.; Mao, Ho-kwang

    2011-01-01

    The structural stability of methane hydrate under pressure at room temperature was examined by both in-situ single-crystal and powder X-ray diffraction techniques on samples with structure types I, II, and H in diamond-anvil cells. The diffraction data for types II (sII) and H (sH) were refined to the known structures with space groups Fd3m and P63/mmc, respectively. Upon compression, sI methane hydrate transforms to the sII phase at 120 MPa, and then to the sH phase at 600 MPa. The sII methane hydrate was found to coexist locally with sI phase up to 500 MPa and with sH phase up to 600 MPa. The pure sH structure was found to be stable between 600 and 900 MPa. Methane hydrate decomposes at pressures above 3 GPa to form methane with the orientationally disordered Fm3m structure and ice VII (Pn3m). The results highlight the role of guest (CH4)-host (H2O) interactions in the stabilization of the hydrate structures under pressure. ?? 2011, China University of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V. All rights reserved.

  10. Hydration status affects osteopontin expression in the rat kidney.

    Science.gov (United States)

    Lee, Su-Youn; Lee, Sae-Jin; Piao, Hong-Lin; Yang, Suk-Young; Weiner, I David; Kim, Jin; Han, Ki-Hwan

    2016-09-30

    Osteopontin (OPN) is a secretory protein that plays an important role in urinary stone formation. Hydration status is associated with the development of urolithiasis. This study was conducted to examine the effects of dehydration and hydration on OPN expression in the rat kidney. Animals were divided into three groups, control, dehydrated, and hydrated. Kidney tissues were processed for light and electron microscope immunocytochemistry, in situhybridization, and immunoblot analysis. Dehydration induced a significant increase in OPN protein expression, whereas increased fluid intake induced a decrease in protein expression. Under control conditions, OPN protein and mRNA expression were only detected in the descending thin limb (DTL). Dehydration induced increased expression in the DTL and the development of detectable expression in the thick ascending limb (TAL). In contrast, OPN expression levels declined to less than the controls in the DTL after hydration, while no expression of either protein or mRNA was detectable in the TAL. Immunoelectron microscopy demonstrated that hydration status altered tubular ultrastructure and intracellular OPN expression in the Golgi apparatus and secretory cytoplasmic vesicles. These data confirm that changes in oral fluid intake can regulate renal tubular epithelial cell OPN expression.

  11. Dynamics of hydrated saccharides of interest in food science

    International Nuclear Information System (INIS)

    Complete text of publication follows. Hydration processes play a relevant role in many fields of fundamental food science, and in industrial food processing. Water determines the presence of dynamic transitions similar to the ones observed in synthetic polymers. The glass transition temperature, TG, in particular, is an important parameter in determining the stability of food systems. A systematic study of the influence of hydration was made on the dynamics of starch and of its main saccharide constituents, amylose and amylopectine, by X-ray, neutron, and Moessbauer γ-ray scattering. Here we report the results of neutron elastic scattering measurements performed on amylose and amylopectine from 20 K to 320 K using the backscattering spectrometer IN13 at the ILL. In the dry samples the temperature dependence of the proton mean square displacement, (u2), shows a harmonic behaviour up to 320 K. For the hydrated samples we observe a low temperature regime (up to ∼230 K for amylose, and ∼250 K for amylopectine) where (u2) is harmonic and almost hydration independent. A 'glass-like' kinetic transition then shows up with a large increase in (u2). The anharmonic contribution to (u2) can be described in terms of conformational transitions in a double well potential. The observed transition temperatures markedly vary with hydration, and they are systematically higher than those observed in globular proteins. (author)

  12. Hydrate prevention in petroleum production sub sea system

    Energy Technology Data Exchange (ETDEWEB)

    Rodrigues, Paula L.F.; Rocha, Humberto A.R. [Universidade Estacio de Sa (UNESA), Rio de Janeiro, RJ (Brazil); Rodrigues, Antonio P. [Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN (Brazil)

    2012-07-01

    In spite of the merits of the several hydrate prevention techniques used nowadays, such as: chemical product injection for inhibition and use of thick thermal insulate lines; hydrates per times happen and they are responsible for considerable production losses. Depressurization techniques can be used so much for prevention as in the remediation. Some hydrate removal techniques need a rig or vessel, resources not readily available and with high cost, reason that limits such techniques just for remediation and not for prevention. In the present work it is proposed and described an innovative depressurization system, remote and resident, for hydrate prevention and removal, applicable as for individual sub sea wells as for grouped wells by manifold. Based on low cost jet pumps, without movable parts and with a high reliability, this technique allows hydrate prevention or remediation in a fast and remote way, operated from the production unit. The power fluid line and fluid return line can be integrated in the same umbilical or annulus line structure, without significant increase in the construction costs and installation. It is not necessary to wait for expensive resource mobilization, sometimes not available quickly, such as: vessels or rigs. It still reduces the chemical product consumption and permits to depressurized stopped lines. Other additional advantage, depressurization procedure can be used in the well starting, removing fluid until riser emptying. (author)

  13. Methane Hydrate Field Program. Development of a Scientific Plan for a Methane Hydrate-Focused Marine Drilling, Logging and Coring Program

    Energy Technology Data Exchange (ETDEWEB)

    Collett, Tim [U.S. Geological Survey, Boulder, CO (United States); Bahk, Jang-Jun [Korea Inst. of Geoscience and Mineral Resources, Daejeon (Korea); Frye, Matt [U.S. Bureau of Ocean Energy Management, Sterling, VA (United States); Goldberg, Dave [Lamont-Doherty Earth Observatory, Palisades, NY (United States); Husebo, Jarle [Statoil ASA, Stavenger (Norway); Koh, Carolyn [Colorado School of Mines, Golden, CO (United States); Malone, Mitch [Texas A & M Univ., College Station, TX (United States); Shipp, Craig [Shell International Exploration and Production Inc., Anchorage, AK (United States); Torres, Marta [Oregon State Univ., Corvallis, OR (United States); Myers, Greg [Consortium For Ocean Leadership Inc., Washington, DC (United States); Divins, David [Consortium For Ocean Leadership Inc., Washington, DC (United States); Morell, Margo [Consortium For Ocean Leadership Inc., Washington, DC (United States)

    2013-12-31

    This topical report represents a pathway toward better understanding of the impact of marine methane hydrates on safety and seafloor stability and future collection of data that can be used by scientists, engineers, managers and planners to study climate change and to assess the feasibility of marine methane hydrate as a potential future energy resource. Our understanding of the occurrence, distribution and characteristics of marine methane hydrates is incomplete; therefore, research must continue to expand if methane hydrates are to be used as a future energy source. Exploring basins with methane hydrates has been occurring for over 30 years, but these efforts have been episodic in nature. To further our understanding, these efforts must be more regular and employ new techniques to capture more data. This plan identifies incomplete areas of methane hydrate research and offers solutions by systematically reviewing known methane hydrate “Science Challenges” and linking them with “Technical Challenges” and potential field program locations.

  14. An effective medium inversion algorithm for gas hydrate quantification and its application to laboratory and borehole measurements of gas hydrate-bearing sediments

    Science.gov (United States)

    Chand, S.; Minshull, T.A.; Priest, J.A.; Best, A.I.; Clayton, C.R.I.; Waite, W.F.

    2006-01-01

    The presence of gas hydrate in marine sediments alters their physical properties. In some circumstances, gas hydrate may cement sediment grains together and dramatically increase the seismic P- and S-wave velocities of the composite medium. Hydrate may also form a load-bearing structure within the sediment microstructure, but with different seismic wave attenuation characteristics, changing the attenuation behaviour of the composite. Here we introduce an inversion algorithm based on effective medium modelling to infer hydrate saturations from velocity and attenuation measurements on hydrate-bearing sediments. The velocity increase is modelled as extra binding developed by gas hydrate that strengthens the sediment microstructure. The attenuation increase is modelled through a difference in fluid flow properties caused by different permeabilities in the sediment and hydrate microstructures. We relate velocity and attenuation increases in hydrate-bearing sediments to their hydrate content, using an effective medium inversion algorithm based on the self-consistent approximation (SCA), differential effective medium (DEM) theory, and Biot and squirt flow mechanisms of fluid flow. The inversion algorithm is able to convert observations in compressional and shear wave velocities and attenuations to hydrate saturation in the sediment pore space. We applied our algorithm to a data set from the Mallik 2L–38 well, Mackenzie delta, Canada, and to data from laboratory measurements on gas-rich and water-saturated sand samples. Predictions using our algorithm match the borehole data and water-saturated laboratory data if the proportion of hydrate contributing to the load-bearing structure increases with hydrate saturation. The predictions match the gas-rich laboratory data if that proportion decreases with hydrate saturation. We attribute this difference to differences in hydrate formation mechanisms between the two environments.

  15. A DFT-based comparative equilibrium study of thermal dehydration and hydrolysis of CaCl₂ hydrates and MgCl₂ hydrates for seasonal heat storage.

    Science.gov (United States)

    Pathak, Amar Deep; Nedea, Silvia; Zondag, Herbert; Rindt, Camilo; Smeulders, David

    2016-04-21

    Salt hydrates store solar energy in chemical form via a reversible dehydration-hydration reaction. However, as a side reaction to dehydration, hydrolysis (HCl formation) may occur in chloride based salt hydrates (specially in MgCl2 hydrates), affecting the durability of the storage system. The mixture of CaCl2 and MgCl2 hydrates has been shown experimentally to have exceptional cycle stability and improved kinetics. However, the optimal operating conditions for the mixture are unknown. To understand the appropriate balance between dehydration and hydrolysis kinetics in the mixtures, it is essential to gain in-depth insight into the mixture components. We present a GGA-DFT level study to investigate the various gaseous structures of CaCl2 hydrates and to understand the relative stability of their conformers. The hydration strength and relative stability of conformers are dominated by electrostatic interactions. A wide network of intramolecular homonuclear and heteronuclear hydrogen bonds is observed in CaCl2 hydrates. Equilibrium product concentrations are obtained during dehydration and hydrolysis reactions under various temperature and pressure conditions. The trend of the dehydration curve with temperature in CaCl2 hydrates is similar to the experiments. Comparing these results to those of MgCl2 hydrates, we find that CaCl2 hydrates are more resistant towards hydrolysis in the temperature range of 273-800 K. Specifically, the present study reveals that the onset temperatures of HCl formation, a crucial design parameter for MgCl2 hydrates, are lower than for CaCl2 hydrates except for the mono-hydrate. PMID:27004734

  16. A DFT-based comparative equilibrium study of thermal dehydration and hydrolysis of CaCl₂ hydrates and MgCl₂ hydrates for seasonal heat storage.

    Science.gov (United States)

    Pathak, Amar Deep; Nedea, Silvia; Zondag, Herbert; Rindt, Camilo; Smeulders, David

    2016-04-21

    Salt hydrates store solar energy in chemical form via a reversible dehydration-hydration reaction. However, as a side reaction to dehydration, hydrolysis (HCl formation) may occur in chloride based salt hydrates (specially in MgCl2 hydrates), affecting the durability of the storage system. The mixture of CaCl2 and MgCl2 hydrates has been shown experimentally to have exceptional cycle stability and improved kinetics. However, the optimal operating conditions for the mixture are unknown. To understand the appropriate balance between dehydration and hydrolysis kinetics in the mixtures, it is essential to gain in-depth insight into the mixture components. We present a GGA-DFT level study to investigate the various gaseous structures of CaCl2 hydrates and to understand the relative stability of their conformers. The hydration strength and relative stability of conformers are dominated by electrostatic interactions. A wide network of intramolecular homonuclear and heteronuclear hydrogen bonds is observed in CaCl2 hydrates. Equilibrium product concentrations are obtained during dehydration and hydrolysis reactions under various temperature and pressure conditions. The trend of the dehydration curve with temperature in CaCl2 hydrates is similar to the experiments. Comparing these results to those of MgCl2 hydrates, we find that CaCl2 hydrates are more resistant towards hydrolysis in the temperature range of 273-800 K. Specifically, the present study reveals that the onset temperatures of HCl formation, a crucial design parameter for MgCl2 hydrates, are lower than for CaCl2 hydrates except for the mono-hydrate.

  17. Effect of changes in seafloor temperature and sea-level on gas hydrate stability

    International Nuclear Information System (INIS)

    Natural gas hydrates occur in oceanic sediments and in permafrost regions around the world. As a greenhouse gas, large amounts of methane released from the global hydrate reservoir would have a significant impact on Earth's climate. The role of methane released by hydrate dissociation in climate change is uncertain. However, changes in global climate such as glaciation and warming can destabilize the hydrates. During the last glacial maximum, the sea level dropped about 100 meters. It has been suggested that the sea-level fall was associated with gas hydrate instability and seafloor slumping. This paper investigated the effect of changes in seafloor temperature and sea level on gas hydrate stability and on gas venting at the seafloor. A one-dimensional numerical computer model (simulator) was developed to describe methane hydrate formation, decomposition, reformation, and distribution with depth below the seafloor in the marine environment. The simulator was utilized to model hydrate distributions at two sites, notably Blake Ridge, located offshore South Carolina and Hydrate Ridge, located off the coast of Oregon. The numerical models for the two sites were conditioned by matching the sulfate, chlorinity, and hydrate distribution measurements. The effect of changes in seafloor temperature and sea-level on gas hydrate stability were then investigated. It was concluded that for Blake Ridge, changes in hydrate concentration were small. Both the changes in seafloor temperature and sea-level led to a substantial increase in gas venting at the seafloor for Hydrate Ridge. 17 refs., 8 figs

  18. Sedimentological control on saturation distribution in Arctic gas-hydrate-bearing sands

    Science.gov (United States)

    Behseresht, Javad; Bryant, Steven L.

    2012-08-01

    A mechanistic model is proposed to predict/explain hydrate saturation distribution in “converted free gas” hydrate reservoirs in sub-permafrost formations in the Arctic. This 1-D model assumes that a gas column accumulates and subsequently is converted to hydrate. The processes considered are the volume change during hydrate formation and consequent fluid phase transport within the column, the descent of the base of gas hydrate stability zone through the column, and sedimentological variations with depth. Crucially, the latter enable disconnection of the gas column during hydrate formation, which leads to substantial variation in hydrate saturation distribution. One form of variation observed in Arctic hydrate reservoirs is that zones of very low hydrate saturations are interspersed abruptly between zones of large hydrate saturations. The model was applied to data from Mount Elbert well, a gas hydrate stratigraphic test well drilled in the Milne Point area of the Alaska North Slope. The model is consistent with observations from the well log and interpretations of seismic anomalies in the area. The model also predicts that a considerable amount of fluid (of order one pore volume of gaseous and/or aqueous phases) must migrate within or into the gas column during hydrate formation. This paper offers the first explanatory model of its kind that addresses “converted free gas reservoirs” from a new angle: the effect of volume change during hydrate formation combined with capillary entry pressure variation versus depth.

  19. Experimental study and modeling of the kinetics of refrigerant hydrate formation

    International Nuclear Information System (INIS)

    Highlights: • The kinetics of the hydrate formation of three refrigerant blends is studied. • The refrigerants include three alternative refrigerants R407C, R410A and R507C. • A kinetic model is developed. • The induction time, apparent rate constant and the rate of hydrate formation are particularly studied. • The effect of sodium dodecyl sulfate (SDS) on the hydrate nucleation rate is investigated. - Abstract: The purpose of this study was to identify compatible hydrate forming-refrigerants suitable for air-conditioning systems. The main challenge in designing an air conditioning system which utilises refrigerant hydrates as a media for storage of cold energy is the rate of formation and dissociation of the refrigerant hydrates. Hence, in this experimental study the kinetics of hydrate formation of three refrigerant blends, viz. R407C, R410A and R507C have been investigated. The induction time for hydrate formation, apparent rate constant of the hydrate reaction, water to hydrate conversion during hydrate growth, storage capacity, and the rate of hydrate formation of these refrigerants at various pressures and temperatures have been obtained using a kinetic model. The effect of sodium dodecyl sulfate (SDS) on the hydrate nucleation rate was also investigated

  20. Investigating the Hydration of CM2 meteorites by IR spectroscopy

    CERN Document Server

    Góbi, S; Beck, P; Quirico, E; Schmidt, B

    2014-01-01

    Chondritic meteorites are of great interest since they are one of the most ancient remnants of the early solar system. Some of them, like the carbonaceous CM meteorites experienced aqueous alteration thus their olivine content transformed more or less into hydrated silicates such as phyllosilicates. These hydrated CM2 meteorites have been investigated in KBr pellets by means of Fourier transform infrared (FT-IR) spectroscopy. In our focus of interest was to study the 3 and 10 $\\mu$m (3000 and 1000 cm$^{-1}$, the O$-$H and silicate streching) bands of several CM2 chondrites. By investigating these signals the water content and the extent of hydration can be determined. In order to achieve this, development of a new pellet production method was essential. This technique facilitates the elimination of adsorbed water coming from the surrounding environment, which would complicate correct interpretation of the results.

  1. Atomistic modelling of the hydration of CaSO 4

    Science.gov (United States)

    Adam, Craig D.

    2003-08-01

    Atomistic modelling techniques, using empirical potentials, have been used to simulate a range of structures formed by the hydration of γ-CaSO 4 and described as CaSO 4· nH 2O (0commercial importance and has been subjected to much experimental study. These simulation studies demonstrate significant water-matrix interactions that influence the crystallography of the hydrated phase. The existence of two types of hydration site has been predicted, including one within the Ca 2+coordination sphere. Close correlation between water molecule bonding energy, Ca 2+-O w bond length and unit-cell volume have been established. This shows that as the number of water molecules within the unit cell increases, the bonding energy increases and the unit cell contracts. However around n=0.5, this process reaches a turning point with the incorporation of further waters resulting in reduced binding energy and an expanding unit cell.

  2. Accelerated growth of calcium silicate hydrates: Experiments and simulations

    International Nuclear Information System (INIS)

    Despite the usefulness of isothermal calorimetry in cement analytics, without any further computations this brings only little information on the nucleation and growth of hydrates. A model originally developed by Garrault et al. is used in this study in order to simulate hydration curves of cement obtained by calorimetry with different known hardening accelerators. The limited basis set of parameters used in this model, having a physical or chemical significance, is valuable for a better understanding of mechanisms underlying in the acceleration of C-S-H precipitation. Alite hydration in presence of four different types of hardening accelerators was investigated. It is evidenced that each accelerator type plays a specific role on one or several growth parameters and that the model may support the development of new accelerators. Those simulations supported by experimental observations enable us to follow the formation of the C-S-H layer around grains and to extract interesting information on its apparent permeability.

  3. Hydration swelling characteristics of needle-punched geosynthetic clay liners

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A series of confined swell tests were conducted on a needle-punched geosynthetic clay liner (GCL)with tap water as the hydration medium. The effects of the static confining stress on the swelling characteristics of GCLs and the hydration time under different confining stresses were explored. Increasing the static confining stress led to: shorter hydration time; smaller final GCL height; less final GCL bulk void ratio; smaller final bentonite moisture content. The confined swell pressure determined for the tested GCL was 82.2 kPa, and the relationships between confining stress, final bulk void ratio (or final GCL height, final bentonite moisture content) were attained through the analyses of the confined swell test results in this study.

  4. Natural gas hydrates and the mystery of the Bermuda Triangle

    Energy Technology Data Exchange (ETDEWEB)

    Gruy, H.J.

    1998-03-01

    Natural gas hydrates occur on the ocean floor in such great volumes that they contain twice as much carbon as all known coal, oil and conventional natural gas deposits. Releases of this gas caused by sediment slides and other natural causes have resulted in huge slugs of gas saturated water with density too low to float a ship, and enough localized atmospheric contamination to choke air aspirated aircraft engines. The unexplained disappearances of ships and aircraft along with their crews and passengers in the Bermuda Triangle may be tied to the natural venting of gas hydrates. The paper describes what gas hydrates are, their formation and release, and their possible link to the mystery of the Bermuda Triangle.

  5. Hydration and swelling of amorphous cross-linked starch microspheres.

    Science.gov (United States)

    Wojtasz, Joanna; Carlstedt, Jonas; Fyhr, Peter; Kocherbitov, Vitaly

    2016-01-01

    Hydration of cross-linked starch microspheres, commercially available as a medical device, was investigated using a multi-method approach. We found that the uptake of water is accompanied by substantial swelling and changes of the polymer structure. Sorption calorimetry provided information about thermodynamics of water sorption, revealed presence of isothermal glass transition and absence of hydration-induced crystallization, observed in non-cross linked starch material. The changes in the surface and bulk properties of microspheres at different water-starch concentrations were investigated using synchrotron radiation X-ray scattering and analyzed using concept of fractals. The obtained information, combined with the results of differential scanning calorimetry, was used to construct a phase diagram of the studied material. Finally, hydration induced evolution of polymer structure revealed by the X-ray scattering was linked to the changes observed during swelling with optical microscopy. PMID:26453872

  6. Temperature dependence of protein hydration hydrodynamics by molecular dynamics simulations.

    Energy Technology Data Exchange (ETDEWEB)

    Lau, E Y; Krishnan, V V

    2007-07-18

    The dynamics of water molecules near the protein surface are different from those of bulk water and influence the structure and dynamics of the protein itself. To elucidate the temperature dependence hydration dynamics of water molecules, we present results from the molecular dynamic simulation of the water molecules surrounding two proteins (Carboxypeptidase inhibitor and Ovomucoid) at seven different temperatures (T=273 to 303 K, in increments of 5 K). Translational diffusion coefficients of the surface water and bulk water molecules were estimated from 2 ns molecular dynamics simulation trajectories. Temperature dependence of the estimated bulk water diffusion closely reflects the experimental values, while hydration water diffusion is retarded significantly due to the protein. Protein surface induced scaling of translational dynamics of the hydration waters is uniform over the temperature range studied, suggesting the importance protein-water interactions.

  7. Synthesis and Antimutagenic Effects of SelenaMorpholine Hydrate

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The synthesis of selenamorpholine hydrate was described and its antimutagenic effects were investigated by the Ames tests. The results indicated that the mutation induced by the indirect mutagen 2-AF was inhibited obviously by selenamorpholine hydrate at the dosage of Se 0. 16~100 μg /dish for 35.8%~53.7%(TA97) and the mutation induced by direct mutagen Dexon was inhibited for 6.2%~30.0%(TA97) and 2.3%~34.1%(TA100). The mutagenesis of the indirect mutagen cyclophosphamide was suppressed for 5.4%~16.1% by selenamorpholine hydrate at the dosage of Se 0. 16~100 μg /dish.

  8. MEMS-based shear characterization of soft hydrated samples

    Science.gov (United States)

    Higgs, Gadryn C.; Simmons, Chelsey S.; Gao, Yingning; Fried, Andrew T.; Park, Sung-Jin; Chung, Cindy; Pruitt, Beth L.

    2013-08-01

    We have designed, fabricated, calibrated and tested actuators for shear characterization to assess microscale shear properties of soft substrates. Here, we demonstrate characterization of dry silicone and hydrated polyethylene glycol. Microscale tools, including atomic force microscopes and nanoindenters, often have limited functionality in hydrated environments. While electrostatic comb-drive actuators are particularly susceptible to moisture damage, through chemical vapor deposition of hexamethyldisiloxane, we increase the hydrophobicity of our electrostatic devices to a water contact angle 90 ± 3°. With this technique, we determine the effective shear stiffness of both dry and hydrated samples for a range of soft substrates. Using computational and analytical models, we compare our empirically determined effective shear stiffness with existing characterization methods, rheology, and nanoindentation, for samples with shear moduli ranging from 5-320 kPa. This work introduces a new approach for microscale assessment of synthetic materials that can be used on biological materials for basic and applied biomaterials research.

  9. Study on synthesis of 15N-hydrazine hydrate

    International Nuclear Information System (INIS)

    The 15N labeled hydrazine hydrate is a strong reducing agent in the synthesis procedure of stable isotope labeled compounds, and it has been widely used in the isotope-labeled pharmaceutical synthesis. The reaction conditions of 15N labeled hydrazine hydrate were mainly investigated by single-factor design, and the following optimized conditions were obtained: the concentration of available chlorine was 115-120 g/L, the chlorination re- action time was 30∼40 min, the reflux time was 7 min, and the mass ratio of material was m(catalyst) : m (urea) = 1.0 : 10.0, and the yield of 15N labeled hydrazine hydrate was 76.1%, the abundance of 15N was 99.20%. (authors)

  10. Structure and Hydration of Highly Branched, Monodisperse Phytoglycogen Nanoparticles

    Science.gov (United States)

    Atkinson, John; Nickels, Jonathan; Stanley, Christopher; Diallo, Souleymane; Katsaras, John; Dutcher, John

    Monodisperse phytoglycogen nanoparticles are a promising, new soft colloidal nanomaterial with many applications in the personal care, food, nutraceutical and pharmaceutical industries. These applications rely on exceptional properties that emerge from the highly branched structure of phytoglycogen and its interaction with water, such as extraordinarily high water retention, and low viscosity and exceptional stability in water. The structure and hydration of the nanoparticles was characterized using small angle neutron scattering (SANS) and quasielastic neutron scattering (QENS). SANS allowed us to determine the size of the nanoparticles, evaluate their radial density profile, quantify the particle-to-particle spacing, and determine their water content. The results show clearly that the nanoparticles are highly hydrated, with each nanoparticle containing 250% of its mass in water, and that aqueous dispersions approach a jamming transition at ~ 25% (w/w). QENS experiments provided an independent and consistent measure of the high level of hydration of the particles.

  11. Geologic implications of gas hydrates in the offshore of India: Krishna-Godavari Basin, Mahanadi Basin, Andaman Sea, Kerala-Konkan Basin

    Digital Repository Service at National Institute of Oceanography (India)

    Kumar, P.; Collett, T.S.; Boswell, R.; Cochran, J.R.; Lall, M.; Mazumdar, A.; Ramana, M.V.; Ramprasad, T.; Riedel, M.; Sain, K.; Sathe, A.V.; Vishwanath, K.; Yadav, U.S.

    Gas hydrate resource assessments that indicate enormous global volumes of gas present within hydrate accumulations have been one of the primary driving forces behind the growing interest in gas hydrates.Gas hydrate volumetric estimates in recent...

  12. Hydration behaviour of food grains and modelling their moisture pick up as per Peleg’s equation: Part I. Cereals

    OpenAIRE

    Vasudeva, Singh; Vishwanathan, K. H.; Aswathanarayana, K. N.; Indhudhara Swamy, Y. M.

    2010-01-01

    Cereals and millets generally hydrate at a moderate rate and their hydration behaviour differs in native and in processed state. The study was on the hydration of paddy, milled rice, parboiled rice, wheat, millets and equilibrium moisture content (EMC) on soaking at room temperature. Paddy hydrated very slowly, hydration rate was slow in brown rice but fast in milled rice and highest in waxy rice. In most of the rice varieties, maximum absorption occurred at the end of 30 min. In wheat hydrat...

  13. The strength and rheology of methane clathrate hydrate

    Science.gov (United States)

    Durham, W.B.; Kirby, S.H.; Stern, L.A.; Zhang, W.

    2003-01-01

    Methane clathrate hydrate (structure I) is found to be very strong, based on laboratory triaxial deformation experiments we have carried out on samples of synthetic, high-purity, polycrystalline material. Samples were deformed in compressional creep tests (i.e., constant applied stress, ??), at conditions of confining pressure P = 50 and 100 MPa, strain rate 4.5 ?? 10-8 ??? ?? ??? 4.3 ?? 10-4 s-1, temperature 260 ??? T ??? 287 K, and internal methane pressure 10 ??? PCH4 ??? 15 MPa. At steady state, typically reached in a few percent strain, methane hydrate exhibited strength that was far higher than expected on the basis of published work. In terms of the standard high-temperature creep law, ?? = A??ne-(E*+PV*)/RT the rheology is described by the constants A = 108.55 MPa-n s-1, n = 2.2, E* = 90,000 J mol-1, and V* = 19 cm3 mol-1. For comparison at temperatures just below the ice point, methane hydrate at a given strain rate is over 20 times stronger than ice, and the contrast increases at lower temperatures. The possible occurrence of syntectonic dissociation of methane hydrate to methane plus free water in these experiments suggests that the high strength measured here may be only a lower bound. On Earth, high strength in hydrate-bearing formations implies higher energy release upon decomposition and subsequent failure. In the outer solar system, if Titan has a 100-km-thick near-surface layer of high-strength, low-thermal conductivity methane hydrate as has been suggested, its interior is likely to be considerably warmer than previously expected.

  14. Ocean Observatory Gas Hydrates Experiments on the Cascadia Margin

    Science.gov (United States)

    Scherwath, Martin; Heesemann, Martin; Mihaly, Steve; Kelley, Deborah; Moran, Kate; Philip, Brendan; Römer, Miriam; Riedel, Michael; Solomon, Evan; Thomsen, Laurenz; Purser, Autun

    2016-04-01

    Ocean Networks Canada's (ONC's) NEPTUNE observatory and the Ocean Observatories Initiative's (OOI's) Cabled Array installations enable long-term gas hydrate experiments on the Cascadia Margin offshore Vancouver Island and Washington and Oregon State. The great advantage of cabled ocean networks in providing power and high bandwidth internet access to the seafloor on a permanent basis is allowing constant monitoring and interacting with experiments hundreds of kilometres away from shore throughout the year. Many different gas hydrate related experiments are installed at three various hydrate nodes, Clayoquot Slope and Barkley Canyon offshore Vancouver Island and Southern Hydrate Ridge offshore Oregon. As an example, a seafloor crawler called Wally is operated from Bremen in Germany by Jacobs University, carrying out measurements by moving around the Barkley hydrate mounds on a daily basis, determining for instance the speed of dynamic changes of the benthic communities. In another example, several years of hourly sonar data show gas bubbles rising from the seafloor near the Bullseye Vent with varying intensities, allowing statistically sound correlations with other seafloor parameters such as ground shaking, temperature and pressure variations and currents, where tidal pressure appearing as the main driver. The Southern Hydrate Ridge is now equipped with the world's first long-term seafloor mass spectrometer, co-located with a camera and lights, hydrophone, current meters, pressure sensor, autonomous OSMO and fluid samplers, and is surrounded by a seismometer array for local seismicity. The data are freely available through open access data portals at: http://dmas.uvic.ca/home and https://ooinet.oceanobservatories.org/

  15. Frozen heat: Global outlook on methane gas hydrates

    Energy Technology Data Exchange (ETDEWEB)

    Beaudoin, Yannick; Solgaard, Anne

    2010-09-15

    The United Nations Environment Programme via its collaborating center in Norway, UNEP/GRID-Arendal, is undertaking an assessment of the state of the knowledge of methane gas hydrates. The Global Outlook on Methane Gas Hydrates seeks to bridge the gap between the science, research and development activities related to this potential large scale unconventional source of natural gas and the needs of decision makers and the general public to understand the underlying societal and environmental drivers and impacts. The Outlook aims to provide credible and unbiased information sourced from stakeholders representing the environment, government, industry and society.

  16. EFFECT OF DIFFERENT OPERATION METHODS ON METHANE HYDRATE FORMATION

    Institute of Scientific and Technical Information of China (English)

    HAO Wenfeng; FAN Shuanshi; WANG Jinqu

    2003-01-01

    Three experiments of static state storage method, low-temperature and constant-pressure storage method and low-temperature and constant-pressure storage method were carried out to investigate which method was best in gas hydrate. The relationships of hydrate rate, capacity and liquid temperature versus time were derived and three results were contrasted. The experimental results show lowtemperature and constant-pressure method is better than the other two methods because it's operation period is shorter and storage capacity is larger than the other two. Low-temperature and constant-pressure method is the best method. So new method will be new research objective.

  17. FIRST BULGARIAN GAS HYDRATES: ASSESSMENT FROM PROBABLE BSRS

    OpenAIRE

    Vasilev, Atanas

    2010-01-01

    This article is a first attempt of gas hydrate study from probable bottom simulating reflectors (BSRs) for the Bulgarian part of the Black Sea. Eleven probable areas of GHs are found. The volumes of GH and methane in them are determined.The new results show the possibility of wide distribution of gas hydrates (GHs) in the area. Additionally the work introduces new challenging tasks concerning global warming impact on GHs and the role of main faults in forecasting oil and gas potential in the ...

  18. Effect of curing temperatura on hydration process of different cement

    OpenAIRE

    Elkhadiri, I.; Palacios, M.; Puertas, F.

    2009-01-01

    [EN]Hydration was studied in two cements (CEM I 42.5R and CEM II/A-V 42.5R) cured at temperatures ranging from 4 to 85°C. Hydration was monitored with a number of instrumental techniques: X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Backscattered Electron (BSE) imaging in conjunction with Energy Dispersive X-ray analysis (EDX) and Nuclear Magnetic Resonance (MAS NMR). The mechanical strength of the pastes was likewise determined at different ages, while mercury int...

  19. Hydration of Portoguese cements, measurement and modelling of chemical shrinkage

    DEFF Research Database (Denmark)

    Maia, Lino; Geiker, Mette Rica; Figueiras, Joaquim A.

    2008-01-01

    Development of cement hydration was studied by measuring the chemical shrinkage of pastes. Five types of Portuguese Portland cement were used in cement pastes with . Chemical shrinkage was measured by gravimetry and dilatometry. In gravimeters results were recorded automatically during at least...... seven days, dilatometers were manually recorded during at least 56 days. The dispersion model was applied to fit chemical shrinkage results and to estimate the maximum (or ultimate) value for calculation of degree of hydration. Except for a pure Portland cement best fits were obtained by the general...

  20. Hofmeister effects: interplay of hydration, nonelectrostatic potentials, and ion size.

    Science.gov (United States)

    Parsons, Drew F; Boström, Mathias; Lo Nostro, Pierandrea; Ninham, Barry W

    2011-07-21

    The classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory of colloids, and corresponding theories of electrolytes, are unable to explain ion specific forces between colloidal particles quantitatively. The same is true generally, for surfactant aggregates, lipids, proteins, for zeta and membrane potentials and in adsorption phenomena. Even with fitting parameters the theory is not predictive. The classical theories of interactions begin with continuum solvent electrostatic (double layer) forces. Extensions to include surface hydration are taken care of with concepts like inner and outer Helmholtz planes, and "dressed" ion sizes. The opposing quantum mechanical attractive forces (variously termed van der Waals, Hamaker, Lifshitz, dispersion, nonelectrostatic forces) are treated separately from electrostatic forces. The ansatz that separates electrostatic and quantum forces can be shown to be thermodynamically inconsistent. Hofmeister or specific ion effects usually show up above ≈10(-2) molar salt. Parameters to accommodate these in terms of hydration and ion size had to be invoked, specific to each case. Ionic dispersion forces, between ions and solvent, for ion-ion and ion-surface interactions are not explicit in classical theories that use "effective" potentials. It can be shown that the missing ionic quantum fluctuation forces have a large role to play in specific ion effects, and in hydration. In a consistent predictive theory they have to be included at the same level as the nonlinear electrostatic forces that form the skeletal framework of standard theory. This poses a challenge. The challenges go further than academic theory and have implications for the interpretation and meaning of concepts like pH, buffers and membrane potentials, and for their experimental interpretation. In this article we overview recent quantitative developments in our evolving understanding of the theoretical origins of specific ion, or Hofmeister effects. These are demonstrated

  1. Gas-hydrates in Krishna-Godavari and Mahanadi basins: New data

    Digital Repository Service at National Institute of Oceanography (India)

    Sain, K.; Ojha, M.; Satyavani, N.; Ramadass, G.A.; Ramprasad, T.; Das, S.K.; Gupta, H.

    . The CDP interval is 12.5 m. References BOSWELL, R. and SAEKI, T. (2010) Motivations for the geophysical investigation of gas hydrates. In: M. Riedel, E. Willoughby, and S. Chopra (Eds.), Geophysical Characterization of Gas Hydrates. Society of Exploration...

  2. Reservoir controls on the occurrence and production of gas hydrates in nature

    Science.gov (United States)

    Collett, Timothy Scott

    2014-01-01

    Gas hydrates in both arctic permafrost regions and deep marine settings can occur at high concentrations in sand-dominated reservoirs, which have been the focus of gas hydrate exploration and production studies in

  3. Methane Hydrate Formation and Dissocation in a Partially Saturated Sand--Measurements and Observations

    Energy Technology Data Exchange (ETDEWEB)

    Kneafsey, Timothy J.; Tomutsa, Liviu; Moridis, George J.; Seol, Yongkoo; Freifeld, Barry; Taylor, Charles E.; Gupta, Arvind

    2005-03-01

    We performed a sequence of tests on a partially water-saturated sand sample contained in an x-ray transparent aluminum pressure vessel that is conducive to x-ray computed tomography (CT) observation. These tests were performed to gather data for estimation of thermal properties of the sand/water/gas system and the sand/hydrate/water/gas systems, as well as data to evaluate the kinetic nature of hydrate dissociation. The tests included mild thermal perturbations for the estimation of the thermal properties of the sand/water/gas system, hydrate formation, thermal perturbations with hydrate in the stability zone, hydrate dissociation through thermal stimulation, additional hydrate formation, and hydrate dissociation through depressurization with thermal stimulation. Density changes throughout the sample were observed as a result of hydrate formation and dissociation, and these processes induced capillary pressure changes that altered local water saturation.

  4. Natural gas hydrates - From a troublemaker to the great white hope?; Erdgashydrate. Vom Stoerenfried zum Hoffnungstraeger?

    Energy Technology Data Exchange (ETDEWEB)

    Nixdorf, J.

    2001-07-01

    The article examines the topic of natural gas hydrates, which have been in discussion for over 60 years. This paper explains under what conditions gas hydrates may form and discusses what action can be taken to prevent their formation where they are not wanted, for example in natural gas transport systems. The paper also reviews the history of research into these hydrates and explains their chemical structure. The role of naturally occurring gas hydrates as a future source of energy is examined. The occurrence of natural gas hydrates in underground as well as off-shore deposits is described and their potential estimated. Methods for the extraction of the hydrates are described and the use of hydrates as a method of gas storage is examined. Further, the relevance of the gas hydrate deposits in permafrost areas in connection with global warming is discussed.

  5. Site Selection for DOE/JIP Gas Hydrate Drilling in the Northern Gulf of Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Collett, T.S. (USGS); Riedel, M. (McGill Univ., Montreal, Quebec, Canada); Cochran, J.R. (Columbia Univ., Palisades, NY); Boswell, R.M.; Kumar, Pushpendra (Oil and Natural Gas Corporation Ltd., Navi Mumbai, India); Sathe, A.V. (Oil and Natural Gas Corporation Ltd., Uttaranchal, INDIA)

    2008-07-01

    Studies of geologic and geophysical data from the offshore of India have revealed two geologically distinct areas with inferred gas hydrate occurrences: the passive continental margins of the Indian Peninsula and along the Andaman convergent margin. The Indian National Gas Hydrate Program (NGHP) Expedition 01 was designed to study the occurrence of gas hydrate off the Indian Peninsula and along the Andaman convergent margin with special emphasis on understanding the geologic and geochemical controls on the occurrence of gas hydrate in these two diverse settings. NGHP Expedition 01 established the presence of gas hydrates in Krishna- Godavari, Mahanadi and Andaman basins. The expedition discovered one of the richest gas hydrate accumulations yet documented (Site 10 in the Krishna-Godavari Basin), documented the thickest and deepest gas hydrate stability zone yet known (Site 17 in Andaman Sea), and established the existence of a fully-developed gas hydrate system in the Mahanadi Basin (Site 19).

  6. Accelerated nucleation of tetrahydrofuran (THF) hydrate in presence of ZIF-61

    Institute of Scientific and Technical Information of China (English)

    Yanhong Wang; Xuemei Lang; Shuanshi Fan

    2012-01-01

    Clathrate hydrate can be used in energy gas storage and transportation,CO2 capture and cool storage etc.However,these technologies are difficult to be used due to the low formation rate and long induction time of hydrate formation.In this paper,ZIF-61 (zeolite imidazolate framework,ZIF) was first used in hydrate formation to stimulate hydrate nucleation.As an additive of clathrate hydrate,ZIF-61 promoted obviously the acceleration of tetrahydrofuran (THF) hydrate nucleation.It shortened the induction time of THF hydrate formation from 2-5 h to 0.3-1 h mainly due to the template function of ZIF-61 by which the nucleation of THF hydrate has been promoted.

  7. Transient seafloor venting on continental slopes from warming-induced methane hydrate dissociation

    Science.gov (United States)

    Darnell, K. N.; Flemings, P. B.

    2015-12-01

    Methane held in frozen hydrate cages within marine sediment comprises one of the largest carbon reservoirs on the planet. Recent submarine observations of widespread methane seepage may record hydrate dissociation due to oceanic warming, which consequently may further amplify climate change. Here we simulate the effect of seafloor warming on marine hydrate deposits using a multiphase flow model. We show that hydrate dissociation, gas migration, and subsequent hydrate formation cangenerate temporary methane venting into the ocean through the hydrate stability zone. Methane seeps venting through the hydrate stability zone on the eastern Atlantic margin may record this process due to warming begun thousands of years ago. Our results contrast with the traditional view that venting occurs only updip of the hydrate stability zone.

  8. The effects of porous medium and temperature on exothermic tetrahydrofuran hydrate formation

    International Nuclear Information System (INIS)

    Highlights: • Temperature profile was obtained for THF hydrate formation in porous media. • Hydrate forms slowly and the heat release is homogeneous in large glass beads. • Exothermic character of THF hydrate formation process is evident. • The effect of initial temperature on the thermal behaviour is small. • Exothermic energy affects the sustained and rapid formation of THF hydrate. - Abstract: Exothermic energy affects the sustained and rapid formation of hydrates. Therefore, it is necessary to clarify the thermal behaviour during hydrate formation. In this study, tetrahydrofuran (THF) was chosen as the hydrate former component due to its low hydrate equilibrium pressure. Five types of glass beads were used to form a porous medium that was saturated with 19 wt% THF solution. Magnetic resonance imaging (MRI) was used to monitor the distribution of the solution in the vessel. The results showed that the “induction time” of THF hydrate formation is short in the glass beads. The exothermic character of the hydrate formation process was evident in the MRI images. The temperature profile in the porous medium was determined based on the MRI mean intensity and temperature. There were obvious higher temperature regions around the hydrate formation zones. It was found that the hydrate formation rate was slowly at multiple points and aggregated in large glass beads, and that the heat release was homogeneous. The residual MI value is higher than that in the small glass beads. Then, the hydrate began to grow from the vessel wall in the small glass beads. The temperature rose significantly during the hydrate formation. The effect of initial temperature on the experimental results is small. There are two factors that cause the temperature rise that cannot be monitored: if hydrate formation is finished and the exothermic energy has been lost, or if the hydrate does not begin to form abundantly

  9. Characteristics of CO2 Hydrate Formation and Dissociation in Glass Beads and Silica Gel

    OpenAIRE

    Qingping Li; Jiafei Zhao; Yu Liu; Xuke Ruan; Yongchen Song; Mingjun Yang

    2012-01-01

    CO 2 hydrate formation and dissociation is crucial for hydrate-based CO 2 capture and storage. Experimental and calculated phase equilibrium conditions of carbon dioxide (CO 2 ) hydrate in porous medium were investigated in this study. Glass beads were used to form the porous medium. The experimental data were generated using a graphical method. The results indicated the decrease of pore size resulted in the increase of the equilibrium pressure of CO 2 hydrate. Magnetic resonance imaging (MRI...

  10. HFC-134a refrigerant gas hydrate formation process and RIN model

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    In this paper, the macroscopic visualization experiments of HFC-134a refrigerant gas hydrate formation are investigated. According to the macroscopic photos and Mori's microscopic photos of HFC-134a hydrate formation process, the mechanism of gas hydrate formation is analyzed.A random inducement nucleation model is presented to describe the hydrate formation process. The factors affecting the fractal growth dimension in the model, such as step,branch increment and angle, are discussed.``

  11. Report: Proceedings of the Hedberg Research Conference 'Gas Hydrates : Energy resource potential and associated geologic hazards'

    Digital Repository Service at National Institute of Oceanography (India)

    Veerayya, M.

    . Timothy Collett, US Geological Survey, Denver Colorado, USA who, besides Dr. Arthur Johnson Hydrate Energy International, New Orleans, LA, USA have played a key role in organizing this conference. This was followed by several technical Oral and Poster... Sessions, covering various aspects of gas hydrates, the main themes being: Technical Oral Sessions: (1) Challenges of Unconventional Resources; (2) Gas Hydrate Resources Development Research; (3) Resource Potential and Geology of Marine Gas Hydrates; (4...

  12. Experimental characterization and modelling of acoustic velocity and electrical resistance in hydrate bearing sediments

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Y.; Zhang, W.; Liu, Y.; Ren, S. [China Univ. of Petroleum, Dongying (China). Inst. of Petroleum Engineering

    2008-07-01

    In the development of gas hydrate resources, characterization of natural gas hydrate bearing sediments is important. Solid hydrates fill the voids of the matrix formed by sand grains and change their cementation condition, which have a significant impact on the resistance and sound velocity of the sand matrix. Acoustic velocity and electrical resistivity are important methods in well-logging of conventional oil/gas reservoirs. They can also be effectively utilized in the characterization of gas hydrate-bearing sediments. Solid hydrates fill the voids between sand grains and change the cementation condition of the sand matrix, which can enhance the propagation of sounds, increasing the sound velocity. Since electric ions are excluded in hydrate, hydrate formation can change the distribution and mobility of electrolytes in sub sea sediments, which will affect the resistance of the sand matrix. This paper presented a study that involved experiments that measured the acoustic P-wave velocity and electrical properties of sandpacks with methane hydrate formed under simulated subsea sediment conditions. The paper discussed the key findings of the experiments in order to correlate the resistivity and acoustic P-wave velocity with hydrate saturation in porous media. The effects of hydrate on the resistivity and ultrasonic velocity of hydrate bearing sand matrix were revealed and modeled. It was concluded that the resistivity of the sandpack bearing with hydrate slightly decreased when hydrate saturation was low, probably because of the hydrate's ion exclusion effect. An increased resistivity with higher hydrate saturation could be explained by a blockage mechanism of hydrates formed in the pores. 11 refs., 1 tab., 8 figs.

  13. A STUDY OF THE HEAT OF HYDRATION OF SULFONIC ACID RESINS

    Institute of Scientific and Technical Information of China (English)

    XURongnan; JIJunyan; 等

    1992-01-01

    The heat of hydration of dry sulfonic acid resin in different comcentrations of sulfuric acid has been determined. The heat of hydration of the resin in H2O is 143.4J/g(resin). The greater the concentration of sulfuric acid,the less the heat will be released.The hydrate formed from three sulfonic acid groups and one water molecule is the most stable one of all the hydrates of sulfonic acid resin and water.

  14. Water in volcanic glass: From volcanic degassing to secondary hydration

    Science.gov (United States)

    Seligman, Angela N.; Bindeman, Ilya N.; Watkins, James M.; Ross, Abigail M.

    2016-10-01

    Volcanic glass is deposited with trace amounts (0.1-0.6 wt.%) of undegassed magmatic water dissolved in the glass. After deposition, meteoric water penetrates into the glass structure mostly as molecular H2O. Due to the lower δD (‰) values of non-tropical meteoric waters and the ∼30‰ offset between volcanic glass and environmental water during hydration, secondary water imparts lighter hydrogen isotopic values during secondary hydration up to a saturation concentration of 3-4 wt.% H2O. We analyzed compositionally and globally diverse volcanic glass from 0 to 10 ka for their δD and H2Ot across different climatic zones, and thus different δD of precipitation, on a thermal conversion elemental analyzer (TCEA) furnace attached to a mass spectrometer. We find that tephrachronologically coeval rhyolite glass is hydrated faster than basaltic glass, and in the majority of glasses an increase in age and total water content leads to a decrease in δD (‰), while a few equatorial glasses have little change in δD (‰). We compute a magmatic water correction based on our non-hydrated glasses, and calculate an average 103lnαglass-water for our hydrated felsic glasses of -33‰, which is similar to the 103lnαglass-water determined by Friedman et al. (1993a) of -34‰. We also determine a smaller average 103lnαglass-water for all our mafic glasses of -23‰. We compare the δD values of water extracted from our glasses to local meteoric waters following the inclusion of a -33‰ 103lnαglass-water. We find that, following a correction for residual magmatic water based on an average δD and wt.% H2Ot of recently erupted ashes from our study, the δD value of water extracted from hydrated volcanic glass is, on average, within 4‰ of local meteoric water. To better understand the difference in hydration rates of mafic and felsic glasses, we imaged 6 tephra clasts ranging in age and chemical composition with BSE (by FEI SEM) down to a submicron resolution. Mafic tephra

  15. Hydration of swelling clays: multi-scale sequence of hydration and determination of macroscopic energies from microscopic properties; Hydratation des argiles gonflantes: sequence d'hydratation multi-echelle determination des energies macroscopiques a partir des proprietes microscopiques

    Energy Technology Data Exchange (ETDEWEB)

    Salles, F

    2006-10-15

    Smectites have interesting properties which make them potential candidates for engineered barriers in deep geological nuclear waste repository: low permeability, swelling and cations retention. The subject of this thesis consists in the determination of the relationship between hydration properties, swelling properties and cations mobility in relation with confinement properties of clayey materials. The aim is to understand and to predict the behaviour of water in smectites, following two research orientations: the mechanistic aspects and the energetic aspects of the hydration of smectites. We worked on the Na-Ca montmorillonite contained in the MX80 bentonite, with the exchanged homo ionic structure (saturated with alkaline cations and calcium cations). The approach crosses the various scales (microscopic, mesoscopic and macroscopic) and implied the study of the various components of the system (layer-cation-water), by using original experimental methods (thermo-poro-metry and electric conductivity for various relative humidities (RH) and electrostatic calculations. Initially, the dry state is defined by SCTA (scanning calorimetry thermal analysis). Then a classical characterization of the smectite porosity for the dry state is carried out using mercury intrusion and nitrogen adsorption. We evidenced the existence of a meso-porosity which radius varies from 2 to 10 nm depending on the compensating cation. The thermo-poro-metry and conductivity experiments performed at various hydration states made it possible to follow the increase in the pore sizes and the cations mobility as a function of the hydration state. We highlight in particular the existence of an osmotic mesoscopic swelling for low RH (approximately 50-60%RH for Li and Na). By combining the results of thermo-poro-metry, X-ray diffraction and electric conductivity, we are able to propose a complete hydration sequence for each cation, showing the crucial role of the compensating cation in the hydration of

  16. Topographic features of gas hydrate mounds of shallow gas hydrate areas in Joetsu Basin , eastern margin of Japan Sea

    Science.gov (United States)

    Hiromatsu, M.; Machiyama, H.; Matsumoto, R.

    2010-12-01

    Mega pockmarks and mounds, both of which are 300m to 500m in diamater and 30m to 40 m deep or high, characterize the Umitaka Spur and Joetsu Knoll of the Joetsu Basin. A number of pockmarks and mounds develop in NNE to SSW direction parallel to the general trend of mobile belt along the eastern margin of Japan Sea, suggesting that the topography has been strongly controlled by regional tectonics. Seismic profiles have revealed well-developed chaotic to transparent zones (gas chimneys) in the area of pockmarks and mounds, from which a number of active methane plumes stand up to 700m above sea floor. Ultra-high resolution bathymetric data and reflection images were acquired by Multi Beam Echo Sounder (MBES) and Side Scan Sonar (SSS) of the AUV "URASHIMA” during the YK10-08 cruise of R/V Yokosuka (JAMSTEC), July 2010. Based on mosaic images of MBES and SSS, we could identify several types of the hydrate mounds over gas chimney zones. Some are represented as a smooth and low bulge without strong reflections of background level, but the others show rough and uneven topography, featured by a few meter scale depressions, crevasses and minor ridges with strong reflector images, indicating the development of hard ground. Such strong reflectors are due to carbonate crusts and concretions and gas hydrate exposures as observed by ROV . Micro-topographic features are likely to represent a growth stage of hydrate mounds, and perhaps the accumulation of shallow gas hydrates. MBES and SSS onboard AUV are powerful tools to identify gas hydrate accumulation and evolution of shallow gas hydrate system.

  17. Methane hydrate dissociation rates as 0.1 MPa and temperatures above 272K

    Energy Technology Data Exchange (ETDEWEB)

    Durham, W B; Circone, S; Stern, L A; Kirby, S H; Pinkston, J C

    1999-10-25

    We performed rapid depressurization experiments on methane hydrate under isothermal conditions above 272 K to determine the amount and rate of methane evolution. Sample temperatures rapidly drop below 273 K and stabilize near 272.5 K during dissociation. This thermal anomaly and the persistence of methane hydrate are consistent with the reported recovery of partially dissociated methane hydrate from ocean drilling cores.

  18. Phase I (CATTS Theory), Phase II (Milne Point), Phase III (Hydrate Ridge)

    Energy Technology Data Exchange (ETDEWEB)

    None, None

    2009-10-31

    This study introduces a new type of cumulative seismic attribute (CATT) which quantifies gas hydrates resources in Hydrate Ridge offshore Oregon. CATT is base on case-specific transforms that portray hydrated reservoir properties. In this study we used a theoretical rock physics model to correct measured velocity log data.

  19. 40 CFR 721.4668 - Hydrated alkaline earth metal salts of metalloid oxyanions.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Hydrated alkaline earth metal salts of... Specific Chemical Substances § 721.4668 Hydrated alkaline earth metal salts of metalloid oxyanions. (a... hydrated alkaline earth metal salts of metalloid oxyanions (PMN P-94-1557) is subject to reporting...

  20. Quantifying Hydrate Formation in Gas-rich Environments Using the Method of Characteristics

    Science.gov (United States)

    You, K.; Flemings, P. B.; DiCarlo, D. A.

    2015-12-01

    Methane hydrates hold a vast amount of methane globally, and have huge energy potential. Methane hydrates in gas-rich environments are the most promising production targets. We develop a one-dimensional analytical solution based on the method of characteristics to explore hydrate formation in such environments (Figure 1). Our solution shows that hydrate saturation is constant with time and space in a homogeneous system. Hydrate saturation is controlled by the initial thermodynamic condition of the system, and changed by the gas fractional flow. Hydrate saturation increases with the initial distance from the hydrate phase boundary. Different gas fractional flows behind the hydrate solidification front lead to different gas saturations at the hydrate solidification front. The higher the gas saturation at the front, the less the volume available to be filled by hydrate, and hence the lower the hydrate saturation. The gas fractional flow depends on the relative permeability curves, and the forces that drive the flow. Viscous forces (the drive for flow induced from liquid pressure gradient) dominate the flow, and hydrate saturation is independent on the gas supply rates and the flow directions at high gas supply rates. Hydrate saturation can be estimated as one minus the ratio of the initial to equilibrium salinity. Gravity forces (the drive for flow induced from the gravity) dominate the flow, and hydrate saturation depends on the flow rates and the flow directions at low gas supply rates. Hydrate saturation is highest for upward flow, and lowest for downward flow. Hydrate saturation decreases with the flow rate for upward flow, and increases with the flow rate for downward flow. This analytical solution illuminates how hydrate is formed by gas (methane, CO2, ethane, propane) flowing into brine-saturated sediments at both the laboratory and geological scales (Figure 1). It provides an approach to generalize the understanding of hydrate solidification in gas

  1. Hydration of swelling clays: multi-scale sequence of hydration and determination of macroscopic energies from microscopic properties

    International Nuclear Information System (INIS)

    Smectites have interesting properties which make them potential candidates for engineered barriers in deep geological nuclear waste repository: low permeability, swelling and cations retention. The subject of this thesis consists in the determination of the relationship between hydration properties, swelling properties and cations mobility in relation with confinement properties of clayey materials. The aim is to understand and to predict the behaviour of water in smectites, following two research orientations: the mechanistic aspects and the energetic aspects of the hydration of smectites. We worked on the Na-Ca montmorillonite contained in the MX80 bentonite, with the exchanged homo ionic structure (saturated with alkaline cations and calcium cations). The approach crosses the various scales (microscopic, mesoscopic and macroscopic) and implied the study of the various components of the system (layer-cation-water), by using original experimental methods (thermo-poro-metry and electric conductivity for various relative humidities (RH) and electrostatic calculations. Initially, the dry state is defined by SCTA (scanning calorimetry thermal analysis). Then a classical characterization of the smectite porosity for the dry state is carried out using mercury intrusion and nitrogen adsorption. We evidenced the existence of a meso-porosity which radius varies from 2 to 10 nm depending on the compensating cation. The thermo-poro-metry and conductivity experiments performed at various hydration states made it possible to follow the increase in the pore sizes and the cations mobility as a function of the hydration state. We highlight in particular the existence of an osmotic mesoscopic swelling for low RH (approximately 50-60%RH for Li and Na). By combining the results of thermo-poro-metry, X-ray diffraction and electric conductivity, we are able to propose a complete hydration sequence for each cation, showing the crucial role of the compensating cation in the hydration of

  2. A Hydration of an Alkyne Illustrating Steam and Vacuum Distillation.

    Science.gov (United States)

    Wasacz, J. P.; Badding, V. G.

    1982-01-01

    Reports on the conversion 2,5-dimethylhexyne-2,5-diol(I) to 2,2,5,5-tetramethyltetrahydrofuran-3-one(II) using aqueous mercuric sulfate without the use of acid. The experiment has been successfully performed in introductory organic chemistry laboratories demonstrating alkyne hydration, steam distillation, vacuum distillation, drying of organic…

  3. Epidermal hydration levels in rosacea patients improve after minocycline therapy.

    LENUS (Irish Health Repository)

    Ní Raghallaigh, S

    2013-12-06

    Patients with rosacea frequently report increased skin sensitivity, with features suggestive of an abnormal stratum corneum (SC) permeability barrier. Sebum, pH and hydration levels influence epidermal homeostasis. The correlation of the change in these parameters with clinically effective treatment has not been previously analysed.

  4. The hydrated electron and its reactions at high temperatures

    DEFF Research Database (Denmark)

    Christensen, Hilbert; Sehested, Knud

    1986-01-01

    The spectrum of the hydrated electron was determined in the temperature range 5-300 "C by using strongly alkaline solutions and high hydrogen pressure. At temperatures up to about 150 "C the temperature coefficients of E, and AE1/2 are -2.8 X and 2 X lo4 eV K-', respectively. E,, is the energy ma...

  5. Cation Hydration Constants by Proton NMR: A Physical Chemistry Experiment.

    Science.gov (United States)

    Smith, Robert L.; And Others

    1988-01-01

    Studies the polarization effect on water by cations and anions. Describes an experiment to illustrate the polarization effect of sodium, lithium, calcium, and strontium ions on the water molecule in the hydration spheres of the ions. Analysis is performed by proton NMR. (MVL)

  6. Simulation of High-Pressure Methane Hydrate Combustion

    Science.gov (United States)

    Popov, Pavel; Sirignano, William

    2015-11-01

    With its prevalence in ocean floor deposits, methane hydrate has recently attracted considerable attention in the combustion community. We present a new scheme for the simulation of methane hydrate combustion at high, near critical pressures. This process features a combination of solid, liquid and gas phases, wherein the solid methane hydrate melts into a bubbly liquid, which then evaporates into a gas phase; methane-air combustion occurs in the gas phase. In addition to its multiphase nature, this problem features the additional challenge of modelling the gas/liquid phase transition at near-critical pressures. A new computational procedure has been developed to simulate this problem, using a detailed chemical mechanism for the simulation of reaction in the gas phase, and featuring a volume-of-fluid (VOF) approach for the simulation of the liquid phase with gas bubbles - a low Stokes number is assumed. This procedure is applied to a laminar shear flow methane hydrate combustion problem. Particular attention is directed to the effects on simulation results of the high-pressure equation of state, liquid/gas phase transition modelling, and the bubbly liquid phase modelling. Simulation results are compared to experimental observations. Supported by AFOSR grant FA9550-12-1-0156, AFOSR scientific manager: Dr. Mitat Birkan.

  7. Gas hydrate dissociation prolongs acidification of the Anthropocene oceans

    NARCIS (Netherlands)

    Boudreau, B.P.; Luo, Yiming; Meysman, Filip J R; Middelburg, J.J.; Dickens, G.R.

    2015-01-01

    Anthropogenic warming of the oceans can release methane (CH4) currently stored in sediments as gas hydrates. This CH4 will be oxidized to CO2, thus increasing the acidification of the oceans. We employ a biogeochemical model of the multimillennial carbon cycle to determine the evolution of the ocean

  8. Hydrated Units in the Martian North Polar Region

    Science.gov (United States)

    Horgan, B. H. N.; Bell, J. F.; Noe Dobrea, E. Z.; Cloutis, E. A.; Bailey, D. T.; Craig, M. A.; Stewart, L.

    2008-03-01

    We show that the hydration signature detected in Olympia Undae extends to other units in the north polar region, including nearly the entirety of the north polar erg, dunes within reentrants in Planum Boreum, and in the north polar layered deposits.

  9. Gas hydrate dissociation prolongs acidification of the Anthropocene oceans

    Science.gov (United States)

    Boudreau, Bernard P.; Luo, Yiming; Meysman, Filip J. R.; Middelburg, Jack J.; Dickens, Gerald R.

    2015-11-01

    Anthropogenic warming of the oceans can release methane (CH4) currently stored in sediments as gas hydrates. This CH4 will be oxidized to CO2, thus increasing the acidification of the oceans. We employ a biogeochemical model of the multimillennial carbon cycle to determine the evolution of the oceanic dissolved carbonate system over the next 13 kyr in response to CO2 from gas hydrates, combined with a reasonable scenario for long-term anthropogenic CO2 emissions. Hydrate-derived CO2 will appreciably delay the neutralization of ocean acidity and the return to preindustrial-like conditions. This finding is the same with CH4 release and oxidation in either the deep ocean or the atmosphere. A change in CaCO3 export, coupled to CH4 release, would intensify the transient rise of the carbonate compensation depth, without producing any changes to the long-term evolution of the carbonate system. Overall, gas hydrate destabilization implies a moderate additional perturbation to the carbonate system of the Anthropocene oceans.

  10. Sorbitol dehydration into isosorbide in a molten salt hydrate medium

    NARCIS (Netherlands)

    Li, J.; Spina, A.; Moulijn, J.A.; Makkee, M.

    2013-01-01

    The sorbitol conversion in a molten salt hydrate medium (ZnCl2; 70 wt% in water) was studied. Dehydration is the main reaction, initially 1,4- and 3,6-anhydrosorbitol are the main products that are subsequently converted into isosorbide; two other anhydrohexitols, (1,5- and 2,5-), formed are in less

  11. Fast x-ray fluorescence microtomography of hydrated biological samples.

    Directory of Open Access Journals (Sweden)

    Enzo Lombi

    Full Text Available Metals and metalloids play a key role in plant and other biological systems as some of them are essential to living organisms and all can be toxic at high concentrations. It is therefore important to understand how they are accumulated, complexed and transported within plants. In situ imaging of metal distribution at physiological relevant concentrations in highly hydrated biological systems is technically challenging. In the case of roots, this is mainly due to the possibility of artifacts arising during sample preparation such as cross sectioning. Synchrotron x-ray fluorescence microtomography has been used to obtain virtual cross sections of elemental distributions. However, traditionally this technique requires long data acquisition times. This has prohibited its application to highly hydrated biological samples which suffer both radiation damage and dehydration during extended analysis. However, recent advances in fast detectors coupled with powerful data acquisition approaches and suitable sample preparation methods can circumvent this problem. We demonstrate the heightened potential of this technique by imaging the distribution of nickel and zinc in hydrated plant roots. Although 3D tomography was still impeded by radiation damage, we successfully collected 2D tomograms of hydrated plant roots exposed to environmentally relevant metal concentrations for short periods of time. To our knowledge, this is the first published example of the possibilities offered by a new generation of fast fluorescence detectors to investigate metal and metalloid distribution in radiation-sensitive, biological samples.

  12. Gas hydrates in gas storage caverns; Gashydrate bei der Gaskavernenspeicherung

    Energy Technology Data Exchange (ETDEWEB)

    Groenefeld, P. [Kavernen Bau- und Betriebs-GmbH, Hannover (Germany)

    1997-12-31

    Given appropriate pressure and temperature conditions the storage of natural gas in salt caverns can lead to the formation of gas hydrates in the producing well or aboveground operating facilities. This is attributable to the stored gas becoming more or less saturated with water vapour. The present contribution describes the humidity, pressure, and temperature conditions conducive to gas hydrate formation. It also deals with the reduction of the gas removal capacity resulting from gas hydrate formation, and possible measures for preventing hydrate formation such as injection of glycol, the reduction of water vapour absorption from the cavern sump, and dewatering of the cavern sump. (MSK) [Deutsch] Bei der Speicherung von Erdgas in Salzkavernen kann es unter entsprechenden Druck- und Temperaturverhaeltnissen zur Gashydratbildung in den Foerdersonden oder obertaegigen Betriebseinrichtungen kommen, weil sich das eingelagerte Gas mehr oder weniger mit Wasserdampf aufsaettigt. Im Folgenden werden die Feuchtigkeits-, Druck- und Temperaturbedingungen, die zur Hydratbildung fuehren erlaeutert. Ebenso werden die Verringerung der Auslagerungskapazitaet durch die Hydratbildung, Massnahmen zur Verhinderung der Hydratbildung wie die Injektion von Glykol, die Verringerung der Wasserdampfaufnahme aus dem Kavernensumpf und die Entwaesserung der Kavernensumpfs selbst beschrieben.

  13. Evaluation of Hydrated Lime Filler in Asphalt Mixtures

    Directory of Open Access Journals (Sweden)

    Mohammed Abbas Hasan Al-Jumaily

    2008-01-01

    Full Text Available Mineral filler is one of important materials and affecting on properties and quality of asphalt mixtures .There are different types of mineral filler depended on cost and quality , the matter encourages us to achieve this study to evaluate hydrated lime filler effects on properties of asphalt mixes related with strength and durability. Conventional asphaltic concrete mixtures with Portland cement and soft sandstone fillers and mixtures modified with hydrated lime were evaluated for their fundamental engineering properties as defined by Marshall properties , index of retained strength , indirect tensile strength , permanent deformation characteristics , and fatigue resistance .A typical dense graded mixture employed in construction of surface course pavement in Iraq in accordance with SCRB specifications was used .The materials used in this study included mineral aggregate materials (coarse and fine sizes were originally obtained from Najaf Sea quarries and two grades of asphalt cements produced from Daurah refinery which are D47 and D66 . The physical properties , stiffness modulus and chemical composition are evaluated for the recovered asphalt cement from prepared asphalt mixes containing various filler types .The paper results indicated that the addition of hydrated lime as mineral filler improved the permanent deformation characteristics and fatigue life and the use of hydrated lime will decrease the moisture susceptibility of the asphalt mixtures.

  14. Modelling the effects of waste components on cement hydration

    NARCIS (Netherlands)

    Eijk, van R.J.; Brouwers, H.J.H.

    2001-01-01

    Ordinary Portland Cement (OPC) is often used for the solidification/stabilization (S/S) of waste containing heavy metals and salts. These waste components will precipitate in the form of insoluble compounds on to unreacted cement clinker grains preventing further hydration. In this study the long te

  15. Modelling the effects of waste components on cement hydration

    NARCIS (Netherlands)

    Eijk, van R.J.; Brouwers, H.J.H.

    2000-01-01

    Ordinary Portland Cement (OPC) is often used for the Solidification/Stabilization (S/S) of waste containing heavy metals and salts. These waste componenents will precipitate in the form of insoluble compounds onto unreacted cement clinker grains preventing further hydration. In this study the long t

  16. The Influence of Hydration on Anaerobic Performance: A Review

    Science.gov (United States)

    Kraft, Justin A.; Green, James M.; Bishop, Phillip A.; Richardson, Mark T.; Neggers, Yasmin H.; Leeper, James D.

    2012-01-01

    This review examines the influence of dehydration on muscular strength and endurance and on single and repeated anaerobic sprint bouts. Describing hydration effects on anaerobic performance is difficult because various exercise modes are dominated by anaerobic energy pathways, but still contain inherent physiological differences. The critical…

  17. A Galvanic Coupling Method for Assessing Hydration Rates

    Directory of Open Access Journals (Sweden)

    Clement Ogugua Asogwa

    2016-07-01

    Full Text Available Recent advances in biomedical sensors, data acquisition techniques, microelectronics and wireless communication systems opened up the use of wearable technology for ehealth monitoring. We introduce a galvanic coupled intrabody communication for monitoring human body hydration. Studies in hydration provide the information necessary for understanding the desired fluid levels for optimal performance of the body’s physiological and metabolic processes during exercise and activities of daily living. Current measurement techniques are mostly suitable for laboratory purposes due to their complexity and technical requirements. Less technical methods such as urine color observation and skin turgor testing are subjective and cannot be integrated into a wearable device. Bioelectrical impedance methods are popular but mostly used for estimating total body water with limited accuracy and sensitive to 800 mL–1000 mL change in body fluid levels. We introduce a non-intrusive and simple method of tracking hydration rates that can detect up to 1.30 dB reduction in attenuation when as little as 100 mL of water is consumed. Our results show that galvanic coupled intrabody signal propagation can provide qualitative hydration and dehydration rates in line with changes in an individual’s urine specific gravity and body mass. The real-time changes in galvanic coupled intrabody signal attenuation can be integrated into wearable electronic devices to evaluate body fluid levels on a particular area of interest and can aid diagnosis and treatment of fluid disorders such as lymphoedema.

  18. Synergistic kinetic inhibition of natural gas hydrate formation

    DEFF Research Database (Denmark)

    Daraboina, Nagu; Malmos, Christine; von Solms, Nicolas

    2013-01-01

    Rocking cells were used to investigate the natural gas hydrate formation and decomposition in the presence of kinetic inhibitor, Luvicap. In addition, the influence of poly ethylene oxide (PEO) and NaCl on the performance of Luvicap was investigated using temperature ramping and isothermal...

  19. Obsidian hydration profile measurements using a nuclear reaction technique

    Science.gov (United States)

    Lee, R.R.; Leich, D.A.; Tombrello, T.A.; Ericson, J.E.; Friedman, I.

    1974-01-01

    AMBIENT water diffuses into the exposed surfaces of obsidian, forming a hydration layer which increases in thickness with time to a maximum depth of 20-40 ??m (ref. 1), this layer being the basic foundation of obsidian dating2,3. ?? 1974 Nature Publishing Group.

  20. Hydrazine hydrate in the reaction of triazine hetero cycle formation

    International Nuclear Information System (INIS)

    In order to understand the mechanism of interaction thiazolidine thiones with hydrazine hydrate which leads to formation of triazine heterocycles the reaction of thiazolidine thiones containing glycolic fragment in 5 position of hetero cycle is conducted. Also for estimation the chemical composition of obtained products the alternative synthesis starting from amido ketone is carried out. (author)

  1. A three-dimensional study on the formation and dissociation of methane hydrate in porous sediment by depressurization

    International Nuclear Information System (INIS)

    Highlights: ► A method to synthesize typical hydrate-bearing samples is proposed. ► Hydrate dissociation in three-dimensional cell occurs throughout the hydrate zone. ► The sharp interface is hardly found during hydrate depressurization dissociation. ► Hydrate dissociation rates at different locations are not uniform. ► Thermal buffering and heat transfer influence on gas production rate of hydrate. - Abstract: A middle-scale reactor equipped with 16 thermocouples was used to investigate the formation and dissociation of methane hydrate in sediment in three dimensions. A method was proposed to form hydrate homogeneously distributed in sediment, i.e., using frozen sand instead of wet sand with pore water. With the formed hydrate sample, hydrate dissociation experiment by depressurization was carried out at a constant pressure of 1.0 MPa. It was found that gas hydrate dissociation occurs throughout the hydrate zone, which controlled by both mass transfer and heat transfer throughout the stages. The sharp-interface is hardly found during the hydrate dissociation. The thermal buffering was observed at the temperature of (271.5–272.2) K during the hydrate dissociation process. The ice arisen from hydrate dissociation slows the hydrate dissociation rate below the ice point, which will affect gas production rate. It may be more reasonable that the depressurization method is used in the initial stage and the thermal stimulation method is used in the later stage in the process of gas recovery from hydrate reservoir.

  2. Methane Hydrate Field Program: Development of a Scientific Plan for a Methane Hydrate-Focused Marine Drilling, Logging and Coring Program

    Energy Technology Data Exchange (ETDEWEB)

    None, None

    2014-02-01

    This final report document summarizes the activities undertaken and the output from three primary deliverables generated during this project. This fifteen month effort comprised numerous key steps including the creation of an international methane hydrate science team, determining and reporting the current state of marine methane hydrate research, convening an international workshop to collect the ideas needed to write a comprehensive Marine Methane Hydrate Field Research Plan and the development and publication of that plan. The following documents represent the primary deliverables of this project and are discussed in summary level detail in this final report: Historical Methane Hydrate Project Review Report; Methane Hydrate Workshop Report; Topical Report: Marine Methane Hydrate Field Research Plan; and Final Scientific/Technical Report.

  3. The Hydration of Subglacial Rhyolite to Form Perlite

    Science.gov (United States)

    Denton, J. S.; Tuffen, H.; Gilbert, J. S.

    2009-12-01

    Subglacial rhyolite deposits at Torfajökull, Iceland encountered glacier meltwater as they cooled, leading to variable amounts of hydration. High-temperature lava-meltwater interactions are key to understanding jökulhlaup hazards, perlite formation, cooling rates and, ultimately, soil formation [Denton et al., 2009]. Perlite is a hydrated glass that contains abundant, intersecting, arcuate and gently curved cracks surrounding cores of intact glass. Knowledge of how perlite forms is required for us to better understand the way in which meltwater and lava interact during and after subglacial eruptions. The mechanism for perlite formation is currently poorly understood, it is not known whether cracking leads to hydration or vice versa. Different textural zones from effusively erupted lava lobes from Torfajökull, Iceland [Tuffen et al., 2001] have been studied using a combination of experimental and quantitative textural measurements to examine the processes of hydration and perlite formation. A differential scanning calorimetry - thermogravimetric analyser coupled to a mass spectrometer (DSC-TGA-MS) has been used to quantify the total volatile contents of a number of samples. A novel petrological technique has been used to quantify the concentration of fractures present in a sample which has then been related to the amount of hydration. Water content using infra-red microspectroscopy (FTIR) has been used to study the micro-scale variations of water content and how they relate to fractures in the rhyolitic glasses. The results indicate that progressive perlitisation at the margins of lava bodies is accompanied by an increase in the water content, from ~0.5 wt. % to ~2 wt. %. The speciation of the inwardly diffusing water changes from hydroxyl to molecular water with increasing total volatile content. The temperature of dehydration of samples during TGA experiments decreases with increasing volatile content, consistent with a change in the dominant H2O species from

  4. Mechanical and electromagnetic properties of northern Gulf of Mexico sediments with and without THF hydrates

    Science.gov (United States)

    Lee, J.Y.; Santamarina, J.C.; Ruppel, C.

    2008-01-01

    Using an oedometer cell instrumented to measure the evolution of electromagnetic properties, small strain stiffness, and temperature, we conducted consolidation tests on sediments recovered during drilling in the northern Gulf of Mexico at the Atwater Valley and Keathley Canyon sites as part of the 2005 Chevron Joint Industry Project on Methane Hydrates. The tested specimens include both unremolded specimens (as recovered from the original core liner) and remolded sediments both without gas hydrate and with pore fluid exchanged to attain 100% synthetic (tetrahydrofuran) hydrate saturation at any stage of loading. Test results demonstrate the extent to which the electromagnetic and mechanical properties of hydrate-bearing marine sediments are governed by the vertical effective stress, stress history, porosity, hydrate saturation, fabric, ionic concentration of the pore fluid, and temperature. We also show how permittivity and electrical conductivity data can be used to estimate the evolution of hydrate volume fraction during formation. The gradual evolution of geophysical properties during hydrate formation probably reflects the slow increase in ionic concentration in the pore fluid due to ion exclusion in closed systems and the gradual decrease in average pore size in which the hydrate forms. During hydrate formation, the increase in S-wave velocity is delayed with respect to the decrease in permittivity, consistent with hydrate formation on mineral surfaces and subsequent crystal growth toward the pore space. No significant decementation/debonding occurred in 100% THF hydrate-saturated sediments during unloading, hence the probability of sampling hydrate-bearing sediments without disturbing the original sediment fabric is greatest for samples in which the gas hydrate is primarily responsible for maintaining the sediment fabric and for which the time between core retrieval and restoration of in situ effective stress in the laboratory is minimized. In evaluating the

  5. Laser Desorption Supersonic Jet Spectroscopy of Hydrated Tyrosine

    Science.gov (United States)

    Oba, Hikari; Shimozono, Yoko; Ishiuchi, Shun-Ichi; Fujii, Masaaki; Carcabal, Pierre

    2013-06-01

    The structure of tyrosine (tyr) consists of amino-acid chain and phenol, and it has roughly two possible binding sites for water, amino-acid site and phenolic OH site. Investigating how water molecule binds to tyr will give fundamental information for hydrations of peptide and protein. Resonance enhanced multi photon ionization (REMPI) spectrum of tyr-water 1:1 cluster has already been reported by de Vries and co-workers, however, no analysis on the hydrated structures has been reported. In the REMPI spectrum, two clusters of bands are observed; one appears at ˜35600 cm^{-1} energy region which is the almost same with 0-0 transitions of tyr monomer, and another is observed at ˜300 cm^{-1} lower than the former. Based on the electronic transition energy of phenylalanine and the hydrated clusters, the former is expected to be derived from a structure that water binds to amino acid site. On the other hand, it is plausibly predicted that the latter originates from a structure that water binds to phenolic OH group, because the electronic transition of mono hydrated phenol is ˜300 cm^{-1} red-shifted from the monomer. We applied IR dip spectroscopy which can measure conformer selective IR spectra to the tyr-(H_{2}O)_{1} clusters by using laser desorption supersonic jet technique to confirm the assignments. Especially in the phenolic OH bound isomer, it was found that the intra molecular hydrogen bond within amino-acid chain, which is far from the water molecule and cannot interact directly with each other, is strengthened by the hydration. A. Abio-Riziq et al., J. Phys. Chem. A, 115, 6077 (2011). Y. Shimozono, et al., Phys. Chem. Chem. Phys., (2013) DOI: 10.1039/c3cp43573c. T. Ebata et al., Phys. Chem. Chem. Phys., 8, 4783 (2006). T. Watanabe et al., J. Chem. Phys., 105, 408 (1996).

  6. Ocean observatory networks monitor gas hydrates systems - Updates from Cascadia

    Science.gov (United States)

    Scherwath, M.; Kelley, D. S.; Moran, K.; Philip, B. T.; Roemer, M.; Riedel, M.; Solomon, E. A.; Spence, G.; Heesemann, M.

    2015-12-01

    Seafloor observatories have been installed at the Cascadia margin with a long-term (>20 year) lifespan. These observatories consist of a variety of node locations cabled back to shore for continuous power and communication to instruments via high bandwidth internet access. Ocean Networks Canada (ONC) maintains two hydrate sites at Barkley Canyon and Clayoquot Slope off Vancouver Island, and the Ocean Observatories Initiative (OOI) Cabled Array connects to Hydrate Ridge off the Oregon coast. Together, these installations comprise a diverse suite of different experiments. For example, a seafloor crawler, operated by Jacobs University in Bremen, travels around the Barkley hydrate mounds on a daily basis and carries out a suite of measurements such as determining the rate of change of the benthic community composition. Another example is from several years of hourly sonar data showing gas bubbles rising from the seafloor near the Bullseye Vent with varying intensities, allowing statistically sound correlations with other seafloor parameters such as ground shaking, temperature and pressure variations and currents, where tidal pressure appearing as the main driver. The Southern Hydrate Ridge is now equipped with the world's first long-term seafloor mass spectrometer, co-located with a camera and lights, hydrophone, current meters, pressure sensor, autonomous dissolved oxygen and fluid samplers, and is surrounded by a seismometer array for local seismicity. In the future, long-term data will be continuously captured and made available throughout the year covering the full range of variations of the dynamic hydrate system, and expect additional experiments to be connected to the observatories from the broader research community.

  7. Improved Design and Fabrication of Hydrated-Salt Pills

    Science.gov (United States)

    Shirron, Peter J.; DiPirro, Michael J.; Canavan, Edgar R.

    2011-01-01

    A high-performance design, and fabrication and growth processes to implement the design, have been devised for encapsulating a hydrated salt in a container that both protects the salt and provides thermal conductance between the salt and the environment surrounding the container. The unitary salt/container structure is known in the art as a salt pill. In the original application of the present design and processes, the salt is, more specifically, a hydrated paramagnetic salt, for use as a refrigerant in a very-low-temperature adiabatic demagnetization refrigerator (ADR). The design and process can also be applied, with modifications, to other hydrated salts. Hydrated paramagnetic salts have long been used in ADRs because they have the desired magnetic properties at low temperatures. They also have some properties, disadvantageous for ADRs, that dictate the kind of enclosures in which they must be housed: Being hydrated, they lose water if exposed to less than 100-percent relative humidity. Because any dehydration compromises their magnetic properties, salts used in ADRs must be sealed in hermetic containers. Because they have relatively poor thermal conductivities in the temperature range of interest (<0.1 K), integral thermal buses are needed as means of efficiently transferring heat to and from the salts during refrigeration cycles. A thermal bus is typically made from a high-thermal-conductivity met al (such as copper or gold), and the salt is configured to make intimate thermal contact with the metal. Commonly in current practice (and in the present design), the thermal bus includes a matrix of wires or rods, and the salt is grown onto this matrix. The density and spacing of the conductors depend on the heat fluxes that must be accommodated during operation.

  8. Animated molecular dynamics simulations of hydrated caesium-smectite interlayers

    Directory of Open Access Journals (Sweden)

    Sposito Garrison

    2002-09-01

    Full Text Available Computer animation of center of mass coordinates obtained from 800 ps molecular dynamics simulations of Cs-smectite hydrates (1/3 and 2/3 water monolayers provided information concerning the structure and dynamics of the interlayer region that could not be obtained through traditional simulation analysis methods. Cs+ formed inner sphere complexes with the mineral surface, and could be seen to jump from one attracting location near a layer charge site to the next, while water molecules were observed to migrate from the hydration shell of one ion to that of another. Neighboring ions maintained a partial hydration shell by sharing water molecules, such that a single water molecule hydrated two ions simultaneously for hundreds of picoseconds. Cs-montmorillonite hydrates featured the largest extent of this sharing interaction, because interlayer ions were able to inhabit positions near surface cavities as well as at their edges, close to oxygen triads. The greater positional freedom of Cs+ within the montmorillonite interlayer, a result of structural hydroxyl orientation and low tetrahedral charge, promoted the optimization of distances between cations and water molecules required for water sharing. Preference of Cs+ for locations near oxygen triads was observed within interlayer beidellite and hectorite. Water molecules also could be seen to interact directly with the mineral surface, entering its surface cavities to approach attracting charge sites and structural hydroxyls. With increasing water content, water molecules exhibited increased frequency and duration of both cavity habitation and water sharing interactions. Competition between Cs+ and water molecules for surface sites was evident. These important cooperative and competitive features of interlayer molecular behavior were uniquely revealed by animation of an otherwise highly complex simulation output.

  9. Guest-Host Interaction Study in Clathrate Hydrates Using Lattice Dynamics Simulation

    Institute of Scientific and Technical Information of China (English)

    Maofeng Jing; Shunle Dong

    2005-01-01

    Lattice dynamics simulation of several gas hydrates (helium, argon, and methane) with different occupancy rates has been performed using TIP3P potential model. Results show that the coupling between the guest and host is not simple as depicted by the conventional viewpoints. For clathrate hydrate enclosing small guest, the small cages are dominantly responsible for the thermodynamic stability of clathrate hydrates. And the spectrum of methane hydrate is studied compared with argon hydrate,then as a result, shrink effect from positive hydrogen shell is proposed.

  10. Portland cement hydration in the presence of admixtures: black gram pulse and superplasticizer

    Directory of Open Access Journals (Sweden)

    Viveka Nand Dwivedi

    2008-12-01

    Full Text Available Effect of admixtures such as black gram pulse (BGP and sulfonated naphthalene based superplasticizer (SP on the hydration of Portland cement has been studied. The hydration characteristics of OPC in the presence of BGP and SP were studied with the help of non evaporable water content determinations, calorimetric method, Mössbauer spectroscopic and atomic force microscopic techniques. Results have shown that both BGP and SP get adsorbed at the surface of cement and its hydration products. The hydration of Portland cement is retarded in the presence of both the admixtures and nanosize hydration products are formed.

  11. Detection of Occupancy Differences in Methane Gas Hydrates by Raman Spectroscopy

    DEFF Research Database (Denmark)

    Hansen, Susanne Brunsgaard; Berg, Rolf W.; Stenby, Erling Halfdan

    2004-01-01

    Gas hydrates are solid crystalline compounds, which grow from micro crystals to bulk masses resembling ordinary slush, snow or ice. Since gas hydrates exist at elevated pressures at temperatures well above the ice point, they can cause severe problems under production and transportation...... of reservoir fluids due to plugging. Methods to prevent hydrate formation are in use, e.g. by injection of inhibitors. From environmental and security points of view an easy way to detect hydrate formation is of interest. We have tried to detect methane hydrate formation by use of Raman spectroscopy....

  12. STUDY OF THE INFLUENCE OF COMPLEMENTARY HYDRATION ON THE MECHANICAL PROPERTIES OF SELF-REDUCING PELLETS

    Directory of Open Access Journals (Sweden)

    Felippe de Oliveira Sousa

    2015-06-01

    Full Text Available This study has investigated how different methods and time of complementary hydration affects the cold strength of self-reducing pellets. Identical pellets had been made by the addition of pellet feed, coal, cement and lime and have been subjected to hydration by water immersion or in a moist chamber for different periods. A group of non-hydrated pellets was used as reference for evaluation the effect of hydration. The pellets were then characterized by mechanical tests of compression and tumbling strength. The results have shown an increase in the mechanical properties of pellets and have proved that the hydration by moist chamber was the most efficient method.

  13. The influence of sedimentation rate variation on the occurrence of methane hydrate crystallized from dissolved methane in marine gas hydrate system

    Science.gov (United States)

    Yuncheng, C.; Chen, D.

    2015-12-01

    Methane is commonly delivered to the gas hydrate stability zone by advection of methane-bearing fluids, diffusion of dissolved methane, and in-situ biogenic methane production (Davie and Buffett, 2003), except at cold vent sites. Burial of pore water and sediment compaction can induce the fluid flux change (Bhatnagar et al., 2007). Sedimentation supply the organic material for methane production. In addition, Gas hydrate can move to below gas hydrate stability zone and decompose via sedimentation. Therefore, sedimentation significantly affect the gas hydrate accumulation. ODP site 997 located at the Blake Ridge. The sedimentation rate is estimated to 48 m/Ma, 245m/Ma, 17.2 m/Ma and 281m/Ma for 0-2.5Ma, 2.5-3.75Ma, 3.75-4.4Ma, and 4.4-5.9Ma, respectively, according to the age-depth profile of biostratigraphic marker of nonnofossils(Paull et al., 1996). We constructed a gas hydrate formation model and apply to ODP sites 997 to evaluate the influence of variation of sedimentation rate on gas hydrate accumulation. Our results show that the gas hydrate format rate varied from 0.013mol/m2-a to 0.017mol/m2-a and the gas hydrate burial to below gas hydrate stability zone varied from 0.001mol/m2-a to 0.018mol/m2-a during recently 5Ma. The gas hydrate formation rate by pore water advection and dissolved methane diffusion would be lower, and the top occurrence of gas hydrate would be shallower, when the sedimentation rate is higher. With higher sedimentation rate, the amount of gas hydrate burial to below stability zone would be larger. The relative high sedimentation rate before 2.5 Ma at ODP site 997 produced the gas hydrate saturation much lower than present value, and over 60% of present gas hydrates are formed during recent 2.5Ma. Reference: Bhatnagar,G., Chapman, W. G.,Dickens, G. R., et al. Generalization of gas hydrate distribution and saturation in marine sediments by scaling of thermodynamic and transport processes. American Journal of Science, 2007, 307, 861

  14. Molecular modeling of the dissociation of methane hydrate in contact with a silica surface.

    Science.gov (United States)

    Bagherzadeh, S Alireza; Englezos, Peter; Alavi, Saman; Ripmeester, John A

    2012-03-15

    We use constant energy, constant volume (NVE) molecular dynamics simulations to study the dissociation of the fully occupied structure I methane hydrate in a confined geometry between two hydroxylated silica surfaces between 36 and 41 Å apart, at initial temperatures of 283, 293, and 303 K. Simulations of the two-phase hydrate/water system are performed in the presence of silica, with and without a 3 Å thick buffering water layer between the hydrate phase and silica surfaces. Faster decomposition is observed in the presence of silica, where the hydrate phase is prone to decomposition from four surfaces, as compared to only two sides in the case of the hydrate/water simulations. The existence of the water layer between the hydrate phase and the silica surface stabilizes the hydrate phase relative to the case where the hydrate is in direct contact with silica. Hydrates bound between the silica surfaces dissociate layer-by-layer in a shrinking core manner with a curved decomposition front which extends over a 5-8 Å thickness. Labeling water molecules shows that there is exchange of water molecules between the surrounding liquid and intact cages in the methane hydrate phase. In all cases, decomposition of the methane hydrate phase led to the formation of methane nanobubbles in the liquid water phase.

  15. Gas hydrate saturation from acoustic impedance and resistivity logs in the shenhu area, south china sea

    Science.gov (United States)

    Wang, X.; Wu, S.; Lee, M.; Guo, Y.; Yang, S.; Liang, J.

    2011-01-01

    During the China's first gas hydrate drilling expedition -1 (GMGS-1), gas hydrate was discovered in layers ranging from 10 to 25 m above the base of gas hydrate stability zone in the Shenhu area, South China Sea. Water chemistry, electrical resistivity logs, and acoustic impedance were used to estimate gas hydrate saturations. Gas hydrate saturations estimated from the chloride concentrations range from 0 to 43% of the pore space. The higher gas hydrate saturations were present in the depth from 152 to 177 m at site SH7 and from 190 to 225 m at site SH2, respectively. Gas hydrate saturations estimated from the resistivity using Archie equation have similar trends to those from chloride concentrations. To examine the variability of gas hydrate saturations away from the wells, acoustic impedances calculated from the 3 D seismic data using constrained sparse inversion method were used. Well logs acquired at site SH7 were incorporated into the inversion by establishing a relation between the water-filled porosity, calculated using gas hydrate saturations estimated from the resistivity logs, and the acoustic impedance, calculated from density and velocity logs. Gas hydrate saturations estimated from acoustic impedance of seismic data are ???10-23% of the pore space and are comparable to those estimated from the well logs. The uncertainties in estimated gas hydrate saturations from seismic acoustic impedances were mainly from uncertainties associated with inverted acoustic impedance, the empirical relation between the water-filled porosities and acoustic impedances, and assumed background resistivity. ?? 2011 Elsevier Ltd.

  16. Three types of gas hydrate reservoirs in the Gulf of Mexico identified in LWD data

    Science.gov (United States)

    Lee, Myung Woong; Collett, Timothy S.

    2011-01-01

    High quality logging-while-drilling (LWD) well logs were acquired in seven wells drilled during the Gulf of Mexico Gas Hydrate Joint Industry Project Leg II in the spring of 2009. These data help to identify three distinct types of gas hydrate reservoirs: isotropic reservoirs in sands, vertical fractured reservoirs in shale, and horizontally layered reservoirs in silty shale. In general, most gas hydratebearing sand reservoirs exhibit isotropic elastic velocities and formation resistivities, and gas hydrate saturations estimated from the P-wave velocity agree well with those from the resistivity. However, in highly gas hydrate-saturated sands, resistivity-derived gas hydrate-saturation estimates appear to be systematically higher by about 5% over those estimated by P-wave velocity, possibly because of the uncertainty associated with the consolidation state of gas hydrate-bearing sands. Small quantities of gas hydrate were observed in vertical fractures in shale. These occurrences are characterized by high formation resistivities with P-wave velocities close to those of water-saturated sediment. Because the formation factor varies significantly with respect to the gas hydrate saturation for vertical fractures at low saturations, an isotropic analysis of formation factor highly overestimates the gas hydrate saturation. Small quantities of gas hydrate in horizontal layers in shale are characterized by moderate increase in P-wave velocities and formation resistivities and either measurement can be used to estimate gas hydrate saturations.

  17. Experimental Study on Mechanism of Depressurizing Dissociation of Methane Hydrate under Saturated Pore Fluid

    Institute of Scientific and Technical Information of China (English)

    Sun Youhong; Su Kai; Guo Wei; Li Bing; Jia Rui

    2016-01-01

    Sediment-hosted hydrate reservoir often contains saturated pore lfuid, which changes the heat transfer and mass transfer characteristics of the hydrate reservoir. The exploitation of hydrate under saturated pore lfuid using depressurization is simulated experimentally to investigate the inlfuence of particle size of porous media, dissociation temperature, pressure drop and injected lfuid type on gas production behavior. Homogeneous methane hydrate was ifrstly formed in frozen quartz sand. With the formed hydrate sample, hydrate dissociation experiments by depressurization were conducted. The test results showed that the gas production rate of hydrate under saturated pore lfuid was substantially inlfuenced by the particle size, the pressure drop and the injected lfuid type, while it was inlfuenced little by the dissociation temperature. The hydrate dissociates faster under larger pressure drop and in the presence of smaller porous media within the experimental region. The dissociation rate increases with an increasing lfuid salinity in the initial stage, while it decreases in the later stage. The increase of gas diffusion resistance resulted from ionic hydration atmosphere in saturated chloride solution impeded the dissociation of hydrate. It can be solved by increasing the pressure drop and decreasing the lfuid salinity in the process of gas recovery from hydrate reservoir.

  18. Effects of Temperature Gradient and Cooling Rate on the Formation of Methane Hydrates in Coarse Sand

    Institute of Scientific and Technical Information of China (English)

    Wang Yingmei; Wu Qingbai; Zhang Peng; Jiang Guanli

    2013-01-01

    Temperature gradient and cooling rate have an obvious effect on formation of methane hydrate. The process for formation of methane hydrate in coarse sand is monitored to understand the relationship between temperature gradient and cooling rate and nucleation, growth and distribution of methane hydrate by using the electrical resistivity method. The results show that the change of resistivity can better relfect the nucleation and growth and distribution of methane hydrate. Temperature gradient promotes the nucleation, formation, and formation rate of methane hydrate. At a temperature gradient of 0.11℃/cm, the rate of methane hydrate formation and saturation reaches a maximum. Cooling rate has little effect on the methane hydrate formation process. Judging from the outcome of ifnal spatial distribution of methane hydrate, the cooling rate has an obvious but irregular effect in coarse sand. The effect of temperature gradient on distribution of methane hydrate in coarse sand is less than that of cooling rate. At a temperature gradient of 0.07℃/cm, methane hydrate is distributed uniformly in the sample. If the temperature gradient is higher or lower than this value, the hydrate is enriched in the upper layer of sample.

  19. Hydrophobic amino acids as a new class of kinetic inhibitors for gas hydrate formation

    Science.gov (United States)

    Sa, Jeong-Hoon; Kwak, Gye-Hoon; Lee, Bo Ram; Park, Da-Hye; Han, Kunwoo; Lee, Kun-Hong

    2013-08-01

    As the foundation of energy industry moves towards gas, flow assurance technology preventing pipelines from hydrate blockages becomes increasingly significant. However, the principle of hydrate inhibition is still poorly understood. Here, we examined natural hydrophobic amino acids as novel kinetic hydrate inhibitors (KHIs), and investigated hydrate inhibition phenomena by using them as a model system. Amino acids with lower hydrophobicity were found to be better KHIs to delay nucleation and retard growth, working by disrupting the water hydrogen bond network, while those with higher hydrophobicity strengthened the local water structure. It was found that perturbation of the water structure around KHIs plays a critical role in hydrate inhibition. This suggestion of a new class of KHIs will aid development of KHIs with enhanced biodegradability, and the present findings will accelerate the improved control of hydrate formation for natural gas exploitation and the utilization of hydrates as next-generation gas capture media.

  20. Methane Hydrate Formation and Dissociation in a PartiallySaturated Core-Scale Sand Sample

    Energy Technology Data Exchange (ETDEWEB)

    Kneafsey, Timothy J.; Tomutsa, Liviu; Moridis, George J.; Seol,Yongkoo; Freifeld, Barry M.; Taylor, Charles E.; Gupta, Arvind

    2005-11-03

    We performed a sequence of tests on a partiallywater-saturated sand sample contained in an x-ray transparent aluminumpressure vessel that is conducive to x-ray computed tomography (CT)observation. These tests were performed to gather data for estimation ofthermal properties of the sand/water/gas system and thesand/hydrate/water/gas systems, as well as data to evaluate the kineticnature of hydrate dissociation. The tests included mild thermalperturbations for the estimation of the thermal properties of thesand/water/gas system, hydrate formation, thermal perturbations withhydrate in the stability zone, hydrate dissociation through thermalstimulation, additional hydrate formation, and hydrate dissociationthrough depressurization with thermal stimulation. Density changesthroughout the sample were observed as a result of hydrate formation anddissociation, and these processes induced capillary pressure changes thataltered local water saturation.

  1. Study on p-Wave Attenuation in Hydrate-Bearing Sediments Based on BISQ Model

    Directory of Open Access Journals (Sweden)

    Chuanhui Li

    2013-01-01

    Full Text Available In hydrate-bearing sediments, the elastic wave attenuation characteristics depend on the elastic properties of the sediments themselves on the one hand, and on the other hand, they also depend on the hydrate occurrence state and hydrate saturation. Since the hydrate-bearing sediments always have high porosity, so they show significant porous medium characteristics. Based on the BISQ porous medium model which is the most widely used model to study the attenuation characteristics in the porous media, we focused on p-wave attenuation in hydrate-bearing sediments in Shenhu Area, South China Sea, especially in specific seismic frequency range, which lays a foundation for the identification of gas hydrates by using seismic wave attenuation in Shenhu Area, South China Sea. Our results depict that seismic wave attenuation is an effective attribute to identify gas hydrates.

  2. Estimating pore-space gas hydrate saturations from well log acoustic data

    Science.gov (United States)

    Lee, Myung W.; Waite, William F.

    2008-01-01

    Relating pore-space gas hydrate saturation to sonic velocity data is important for remotely estimating gas hydrate concentration in sediment. In the present study, sonic velocities of gas hydrate–bearing sands are modeled using a three-phase Biot-type theory in which sand, gas hydrate, and pore fluid form three homogeneous, interwoven frameworks. This theory is developed using well log compressional and shear wave velocity data from the Mallik 5L-38 permafrost gas hydrate research well in Canada and applied to well log data from hydrate-bearing sands in the Alaskan permafrost, Gulf of Mexico, and northern Cascadia margin. Velocity-based gas hydrate saturation estimates are in good agreement with Nuclear Magneto Resonance and resistivity log estimates over the complete range of observed gas hydrate saturations.

  3. Experimental study of separation of ammonia synthesis vent gas by hydrate formation

    Institute of Scientific and Technical Information of China (English)

    Dong Taibin; Wang Leiyan; Liu Aixian; Guo Xuqiang; Ma Qinglan; Li Guowen; Sun Qiang

    2009-01-01

    Termodynamic data on methane hydrate formation in the presence of ammonia are very important for upgrading of ammonia synthesis vent gas using hydrate formation.This paper is focused on the formation conditions of methane hydrate in the presence of ammonia and the effects of gas-liquid ratio and temperature on the separation of vent gas by hydrate formation.Equilibrium data for methane hydrate within an ammonia mole concentration range from 1% to 5 % were obtained.The experimental results indicated that ammonia has an inhibitive effect on hydrate formation.The higher the ammonia concentration, the higher is the pressure reguired for methane hydrate formation would be.The primary experimental results showed that when volume ratio of gas to liquid was 80:1 and temperature was 283.15 K, total mole fraction of (H2+N2) in gas phase could reach 96.9 %.

  4. Methane Hydrate Formation and Dissociation in the Presence of Silica Sand and Bentonite Clay

    Directory of Open Access Journals (Sweden)

    Kumar Saw V.

    2015-11-01

    Full Text Available The formation and dissociation of methane hydrates in a porous media containing silica sand of different sizes and bentonite clay were studied in the presence of synthetic seawater with 3.55 wt% salinity. The phase equilibrium of methane hydrate under different experimental conditions was investigated. The effects of the particle size of silica sand as well as a mixture of bentonite clay and silica sand on methane hydrate formation and its dissociation were studied. The kinetics of hydrate formation was studied under different subcooling conditions to observe its effects on the induction time of hydrate formation. The amount of methane gas encapsulated in hydrate was computed using a real gas equation. The Clausius-Clapeyron equation is used to estimate the enthalpy of hydrate dissociation with measured phase equilibrium data.

  5. Geophysical Indicators of Gas Hydrate in the Northern Continental Margin, South China Sea

    Directory of Open Access Journals (Sweden)

    Xiujuan Wang

    2011-01-01

    Full Text Available Gas hydrate drilling results show that gas hydrate has a close relationship with strong bottom-simulating reflectors (BSRs identified from seismic data in the Baiyun sag, South China Sea. The BSRs observed on seismic profiles at the crests of submarine canyons indicate the likely existence of gas hydrate. We calculate the acoustic impedance using constrained sparse spike inversion (CSSI, the interval velocity, and the seismic reflection characteristics such as reflection strength, instantaneous frequency, blanking, and enhanced reflection to demonstrate the presence of gas hydrate. Higher acoustic impedance and P-wave velocity were identified above the BSR. A remarkable low impedance, low frequency, and acoustic blanking indicated the presence of gas below gas hydrate stability zone. The occurrence of gas hydrate at the crests of canyons suggests that the abundance of gas hydrate in Baiyun sag may be due to the migrating submarine canyons providing the structural reliefs and the topographic ridges.

  6. Micromechanical measurements of the effect of surfactants on cyclopentane hydrate shell properties.

    Science.gov (United States)

    Brown, Erika P; Koh, Carolyn A

    2016-01-01

    Investigating the effect of surfactants on clathrate hydrate growth and morphology, especially particle shell strength and cohesion force, is critical to advancing new strategies to mitigate hydrate plug formation. In this study, dodecylbenzenesulfonic acid and polysorbate 80 surfactants were included during the growth of cyclopentane hydrates at several concentrations above and below the critical micelle concentration. A novel micromechanical method was applied to determine the force required to puncture the hydrate shell using a glass cantilever (with and without surfactants), with annealing times ranging from immediately after the hydrate nucleated to 90 minutes after formation. It was shown that the puncture force was decreased by the addition of both surfactants up to a maximum of 79%. Over the entire range of annealing times (0-90 minutes), the thickness of the hydrate shell was also measured. However, there was no clear change in shell thickness with the addition of surfactants. The growth rate of the hydrate shell was found to vary less than 15% with the addition of surfactants. The cohesive force between two hydrate particles was measured for each surfactant and found to be reduced by 28% to 78%. Interfacial tension measurements were also performed. Based on these results, microscopic changes to the hydrate shell morphology (due to the presence of surfactants) were proposed to cause the decrease in the force required to break the hydrate shell, since no macroscopic morphology changes were observed. Understanding the hydrate shell strength can be critical to reducing the capillary bridge interaction between hydrate particles or controlling the release of unconverted water from the interior of the hydrate particle, which can cause rapid hydrate conversion.

  7. Micromechanical measurements of the effect of surfactants on cyclopentane hydrate shell properties.

    Science.gov (United States)

    Brown, Erika P; Koh, Carolyn A

    2016-01-01

    Investigating the effect of surfactants on clathrate hydrate growth and morphology, especially particle shell strength and cohesion force, is critical to advancing new strategies to mitigate hydrate plug formation. In this study, dodecylbenzenesulfonic acid and polysorbate 80 surfactants were included during the growth of cyclopentane hydrates at several concentrations above and below the critical micelle concentration. A novel micromechanical method was applied to determine the force required to puncture the hydrate shell using a glass cantilever (with and without surfactants), with annealing times ranging from immediately after the hydrate nucleated to 90 minutes after formation. It was shown that the puncture force was decreased by the addition of both surfactants up to a maximum of 79%. Over the entire range of annealing times (0-90 minutes), the thickness of the hydrate shell was also measured. However, there was no clear change in shell thickness with the addition of surfactants. The growth rate of the hydrate shell was found to vary less than 15% with the addition of surfactants. The cohesive force between two hydrate particles was measured for each surfactant and found to be reduced by 28% to 78%. Interfacial tension measurements were also performed. Based on these results, microscopic changes to the hydrate shell morphology (due to the presence of surfactants) were proposed to cause the decrease in the force required to break the hydrate shell, since no macroscopic morphology changes were observed. Understanding the hydrate shell strength can be critical to reducing the capillary bridge interaction between hydrate particles or controlling the release of unconverted water from the interior of the hydrate particle, which can cause rapid hydrate conversion. PMID:26618773

  8. Geomechanical Performance of Hydrate-Bearing Sediments in Offshore Environments

    Energy Technology Data Exchange (ETDEWEB)

    Stephen A. Holditch

    2006-12-31

    The main objective of this study is to develop the necessary knowledge base and quantitative predictive capability for the description of geomechanical performance of hydrate bearing sediments (hereafter referred to as HBS) in oceanic environments. The focus is on the determination of the envelope of hydrate stability under conditions typical of those related to the construction and operation of offshore platforms. To achieve this objective, we have developed a robust numerical simulator of hydrate behavior in geologic media by coupling a reservoir model with a commercial geomechanical code. To be sure our geomechanical modeling is realistic, we are also investigating the geomechanical behavior of oceanic HBS using pore-scale models (conceptual and mathematical) of fluid flow, stress analysis, and damage propagation. In Phase II of the project, we will review all published core data and generate additional core data to verify the models. To generate data for our models, we are using data from the literature and we will be conducting laboratory studies in 2007 that generate data to (1) evaluate the conceptual pore-scale models, (2) calibrate the mathematical models, (3) determine dominant relations and critical parameters defining the geomechanical behavior of HBS, and (4) establish relationships between the geomechanical status of HBS and the corresponding geophysical signature. The milestones for Phase I of this project are given as follows: Literature survey on typical sediments containing gas hydrates in the ocean (TAMU); Recommendations on how to create typical sediments in the laboratory (TAMU); Demonstrate that typical sediments can be created in a repeatable manner in the laboratory and gas hydrates can be created in the pore space (TAMU); Develop a conceptual pore-scale model based on available data and reports (UCB); Test the developed pore-scale concepts on simple configurations and verify the results against known measurements and observations (UCB

  9. Comparison of the physical and geotechnical properties of gas-hydrate-bearing sediments from offshore India and other gas-hydrate-reservoir systems

    Science.gov (United States)

    Winters, William J.; Wilcox-Cline, R.W.; Long, P.; Dewri, S.K.; Kumar, P.; Stern, Laura A.; Kerr, Laura A.

    2014-01-01

    The sediment characteristics of hydrate-bearing reservoirs profoundly affect the formation, distribution, and morphology of gas hydrate. The presence and type of gas, porewater chemistry, fluid migration, and subbottom temperature may govern the hydrate formation process, but it is the host sediment that commonly dictates final hydrate habit, and whether hydrate may be economically developed.In this paper, the physical properties of hydrate-bearing regions offshore eastern India (Krishna-Godavari and Mahanadi Basins) and the Andaman Islands, determined from Expedition NGHP-01 cores, are compared to each other, well logs, and published results of other hydrate reservoirs. Properties from the hydrate-free Kerala-Konkan basin off the west coast of India are also presented. Coarser-grained reservoirs (permafrost-related and marine) may contain high gas-hydrate-pore saturations, while finer-grained reservoirs may contain low-saturation disseminated or more complex gas-hydrates, including nodules, layers, and high-angle planar and rotational veins. However, even in these fine-grained sediments, gas hydrate preferentially forms in coarser sediment or fractures, when present. The presence of hydrate in conjunction with other geologic processes may be responsible for sediment porosity being nearly uniform for almost 500 m off the Andaman Islands.Properties of individual NGHP-01 wells and regional trends are discussed in detail. However, comparison of marine and permafrost-related Arctic reservoirs provides insight into the inter-relationships and common traits between physical properties and the morphology of gas-hydrate reservoirs regardless of location. Extrapolation of properties from one location to another also enhances our understanding of gas-hydrate reservoir systems. Grain size and porosity effects on permeability are critical, both locally to trap gas and regionally to provide fluid flow to hydrate reservoirs. Index properties corroborate more advanced

  10. Rheological properties of hydrate suspensions in asphaltenic crude oils; Proprietes rheologiques de suspensions d'hydrate dans des bruts asphalteniques

    Energy Technology Data Exchange (ETDEWEB)

    Marques de Toledo Camargo, R.

    2001-03-01

    The development of offshore oil exploitation under increasing water depths has forced oil companies to increase their understanding of gas hydrate formation and transportation in multiphase flow lines in which a liquid hydrocarbon phase is present. This work deals with the flow behaviour of hydrate suspensions in which a liquid hydrocarbon is the continuous phase. Three different liquid hydrocarbons are used: an asphaltenic crude oil, a condensate completely free of asphaltenes and a mixture between the asphaltenic oil and heptane. The rheological characterisation of hydrate suspensions is the main tool employed. Two original experimental devices are used: a PVT cell adapted to operate as a Couette type rheometer and a semi-industrial flow loop. Hydrate suspensions using the asphaltenic oil showed shear-thinning behaviour and thixotropy. This behaviour is typically found in flocculated systems, in which the particles attract each other forming flocs of aggregated particles at low shear rates. The suspensions using the condensate showed Newtonian behaviour. Their relative viscosities were high, which suggests that an aggregation process between hydrate particles takes. place during hydrate formation. Finally, hydrate suspensions using the mixture asphaltenic oil-heptane showed shear-thinning behaviour, thixotropy and high relative viscosity. From these results it can be inferred that, after the achievement of the hydrate formation process, the attractive forces between hydrate particles are weak. making unlikely pipeline obstruction by an aggregation process. Nevertheless, during the hydrate formation, these attractive forces can be sufficiently high. It seems that the hydrate surface wettability is an important parameter in this phenomena. (author)

  11. TOUGH+Hydrate v1.0 User's Manual: A Code for the Simulation of System Behavior in Hydrate-Bearing Geologic Media

    Energy Technology Data Exchange (ETDEWEB)

    Moridis, George; Moridis, George J.; Kowalsky, Michael B.; Pruess, Karsten

    2008-03-01

    TOUGH+HYDRATE v1.0 is a new code for the simulation of the behavior of hydrate-bearing geologic systems. By solving the coupled equations of mass and heat balance, TOUGH+HYDRATE can model the non-isothermal gas release, phase behavior and flow of fluids and heat under conditions typical of common natural CH{sub 4}-hydrate deposits (i.e., in the permafrost and in deep ocean sediments) in complex geological media at any scale (from laboratory to reservoir) at which Darcy's law is valid. TOUGH+HYDRATE v1.0 includes both an equilibrium and a kinetic model of hydrate formation and dissociation. The model accounts for heat and up to four mass components, i.e., water, CH{sub 4}, hydrate, and water-soluble inhibitors such as salts or alcohols. These are partitioned among four possible phases (gas phase, liquid phase, ice phase and hydrate phase). Hydrate dissociation or formation, phase changes and the corresponding thermal effects are fully described, as are the effects of inhibitors. The model can describe all possible hydrate dissociation mechanisms, i.e., depressurization, thermal stimulation, salting-out effects and inhibitor-induced effects. TOUGH+HYDRATE is the first member of TOUGH+, the successor to the TOUGH2 [Pruess et al., 1991] family of codes for multi-component, multiphase fluid and heat flow developed at the Lawrence Berkeley National Laboratory. It is written in standard FORTRAN 95, and can be run on any computational platform (workstation, PC, Macintosh) for which such compilers are available.

  12. Imaging hydrated microbial extracellular polymers: Comparative analysis by electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Dohnalkova, A.C.; Marshall, M. J.; Arey, B. W.; Williams, K. H.; Buck, E. C.; Fredrickson, J. K.

    2011-01-01

    Microbe-mineral and -metal interactions represent a major intersection between the biosphere and geosphere but require high-resolution imaging and analytical tools for investigating microscale associations. Electron microscopy has been used extensively for geomicrobial investigations and although used bona fide, the traditional methods of sample preparation do not preserve the native morphology of microbiological components, especially extracellular polymers. Herein, we present a direct comparative analysis of microbial interactions using conventional electron microscopy approaches of imaging at room temperature and a suite of cryogenic electron microscopy methods providing imaging in the close-to-natural hydrated state. In situ, we observed an irreversible transformation of the hydrated bacterial extracellular polymers during the traditional dehydration-based sample preparation that resulted in their collapse into filamentous structures. Dehydration-induced polymer collapse can lead to inaccurate spatial relationships and hence could subsequently affect conclusions regarding nature of interactions between microbial extracellular polymers and their environment.

  13. Thermally induced evolution of phase transformations in gas hydrate sediment

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Thermally induced evolution of phase transformations is a basic physical-chemical process in the dissociation of gas hydrate in sediment (GHS). Heat transfer leads to the weakening of the bed soil and the simultaneous establishment of a time varying stress field accompanied by seepage of fluids and deformation of the soil. As a consequence, ground failure could occur causing engineering damage or/and environmental disaster. This paper presents a simplified analysis of the thermal process by assuming that thermal conduction can be decoupled from the flow and deformation process. It is further assumed that phase transformations take place instantaneously. Analytical and numerical results are given for several examples of simplified geometry. Experiments using Tetra-hydro-furan hydrate sediments were carried out in our laboratory to check the theory. By comparison, the theoretical, numerical and experimental results on the evolution of dissociation fronts and temperature in the sediment are found to be in good agreement.

  14. Radiation-induced radicals in hydrated magnesium sulfate

    International Nuclear Information System (INIS)

    Radiation-induced free radicals in hydrated magnesium sulfate, which are thought to be present on the surface of Europa, one of the Jovian moons, have been studied by electron spin resonance (ESR). ESR signals of both atomic hydrogen (H·) at g = 2.0023 and sulfite radical (SO3−·) at g = 2.0029 are observed in epsomite (MgSO4·7H2O) and in quenched samples of magnesium sulfate solutions, after gamma-ray irradiation at 77 K. Atomic hydrogen disappears at temperatures above 90 K. The sulfite radical starts to decay above 190 K in the quenched sample of 10% magnesium sulfate solution, whereas in epsomite, it is stable even at 260 K. The sulfite radical accumulates at low ambient temperatures, and is a promising candidate for estimating the age of hydrated magnesium sulfate, especially in extraterrestrial environments.

  15. Geochemical Evidence for Gas Hydrates in the Indian Ocean

    Science.gov (United States)

    Kastner, M.; Solomon, E.; Torres, M.; Spivack, A. J.; Borole, D. V.; Hangsterfer, A.; Das, H. C.; Robertson, G. A.

    2007-12-01

    Geochemical analyses of pore fluids collected from both non-pressurized and pressurized cores provide important constraints on the presence and distribution of gas hydrates in the Indian Ocean. Cores were recovered from two deepwater (900-1170 meter) basins offshore southeast India, the Krishna-Godavari (KG) (10 sites) and Mahanadi Basins (2 sites), and from one site in the Andaman Sea (1600 meters water depth). A bottom simulating reflector (BSR) (i.e., possible base of methane hydrate stability) was present at most of the sites cored and evidence for methane hydrate was obtained at each of the sites. The gas hydrates in most of the conventional cores decomposed prior to sampling. The former presence and distribution of methane hydrate in some of the conventional cores was inferred by indirect methods: from infra-red imaging of cold core temperatures that correlated with pore fluids having lower salinity and chloride concentrations and occasionally mousse-like textures. Chloride concentrations and salinity anomalies, assuming dilution by water released from decomposed methane hydrate, suggest pore volume occupancies on the order of, methane hydrate concentrations were associated with fracture zones in clay/silt sediments or in some coarser grained horizons, although gas hydrate was not present in all coarse- grained sediment horizons. Overall, the % occupancies based on pressure core methane concentrations and the chloride concentrations in conventional cores were similar. The pressure core samples used for these determinations were 1 m long, and the conventional core samples were 10-30 cm whole round core samples, chosen via IR imaging. Variations in sulfate gradients were observed; the steepest gradient with the sulfate/methane interface (SMI) at 8 mbsf was observed in the KG Basin. The deepest SMI obtained, at 25 mbsf, was documented at the Andaman Sea site. The shallow depths of the SMI at all sites indicate that methane advection is intense. The extreme

  16. Absolute Hydration Free Energies of Ions Under Periodic Boundary Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Won, Youngdo [Hanyang Univ., Seoul (Korea, Republic of)

    2012-12-15

    The additive empirical force field of a monatomic ion is composed of the charge and the Lennard-Jones (LJ) parameters, i. e., the well-depth parameter, ε, and the distance parameter, R{sub min}, at which the potential reaches the minimum. A set of LJ parameters for monocations have been developed by utilizing molecular dynamics simulations under a solvent boundary potential (SBP). A full account of the force field development is in progress and this communication addresses consideration of the air-water phase potential in calculating the absolute free energy of hydration by calculating free energies of hydration, ΔG{sub hyd}, in the presence of periodic boundary conditions (PBC)

  17. Hydration of Kr(aq) in Dilute and Concentrated Solutions.

    Science.gov (United States)

    Chaudhari, Mangesh I; Sabo, Dubravko; Pratt, Lawrence R; Rempe, Susan B

    2015-07-23

    Molecular dynamics simulations of water with both multi-Kr and single Kr atomic solutes are carried out to implement quasi-chemical theory evaluation of the hydration free energy of Kr(aq). This approach obtains free energy differences reflecting Kr-Kr interactions at higher concentrations. Those differences are negative changes in hydration free energies with increasing concentrations at constant pressure. The changes are due to a slight reduction of packing contributions in the higher concentration case. The observed Kr-Kr distributions, analyzed with the extrapolation procedure of Krüger et al., yield a modestly attractive osmotic second virial coefficient, B2 ≈ -60 cm(3)/mol. The thermodynamic analysis interconnecting these two approaches shows that they are closely consistent with each other, providing support for both approaches.

  18. Investigation of sodium iodide hydration and dehydration in moist atmosphere

    International Nuclear Information System (INIS)

    Effect of different factors on NaI hydration and dehydration kinetics under nonequilibrium conditions is studied. NaIx2H2O solid or homogeneous solution is established to be formed at sodium iodide interaction with water vapour depending on air humidity. At low humidity water absorption is not observed. Effect of water vapour pressure, the NaI particle size, the air flux rate over a salt on the absorption rate is studied. The latter points to process rate limitation by diffusion in a gaseous phase. The NaI solution decomposition at light with iodine formation is marked. The character of NaIx2H2O dehydration depends on water vapour removing from the over-salt space. Total water removing before and after crystal hydrate thermal degradation when aqueous solution evaporation occurs, is possible. At 143 deg C the water vapour pressure over solution equals the atmospheric one

  19. Hydration and thermal strain during tennis in the heat

    Science.gov (United States)

    Bergeron, Michael F

    2014-01-01

    Competitive tennis in the heat can prompt substantial sweat losses and extensive consequent body water and electrolyte deficits, as well as a level of thermal strain that considerably challenges a player's physiology, perception of effort, and on-court well-being and performance. Adequate hydration and optimal performance can be notably difficult to maintain when multiple same-day matches are played on successive days in hot weather. Despite the recognised effects of the heat, much more research needs to be carried out to better appreciate the broader scope and full extent of the physiological demands and hydration and thermal strain challenges facing junior and adult players in various environments, venues and competition scenarios. However, certain recommendations of best practices should be emphasised to minimise exertional heat illness risk and improve player safety, well-being and on-court performance. PMID:24668373

  20. Molecular dynamics of poly(N-vinylcaprolactam) hydrate

    CERN Document Server

    Lebedev, V T; Toeroek, G; Cser, L; Kali, G

    2002-01-01

    Poly(N-vinylcaprolactam)-D sub 2 O has been studied by Neutron Spin Echo (NSE) in the temperature range from -60 C to +40 C. Hydration (propor to 7 D sub 2 O molecules per chain unit) transforms the rigid-chain polymer into an elastomer, making the glass-transition temperature drop from T sub G =147 C (dry polymer) to T sub G =-20 C. The hydration shell, created by hydrogen bonds of water molecules with C=O groups, remains stable up to propor to 50 C. The molecular mobility is enhanced by the addition of water, showing a maximum in the window T=-20 to +5 C. The anomalous dynamics was studied in the time domain t=0.003-5 ns (momentum transfer q=0.55 nm sup - sup 1), and demonstrated the hybridisation of transversal modes and reputations of the chains. (orig.)

  1. Numerical simulations of CO2 -assisted gas production from hydrate reservoirs

    Science.gov (United States)

    Sridhara, P.; Anderson, B. J.; Myshakin, E. M.

    2015-12-01

    A series of experimental studies over the last decade have reviewed the feasibility of using CO2 or CO2+N2 gas mixtures to recover CH4 gas from hydrates deposits. That technique would serve the dual purpose of CO2 sequestration and production of CH4 while maintaining the geo-mechanical stability of the reservoir. In order to analyze CH4 production process by means of CO2 or CO2+N2 injection into gas hydrate reservoirs, a new simulation tool, Mix3HydrateResSim (Mix3HRS)[1], was previously developed to account for the complex thermodynamics of multi-component hydrate phase and to predict the process of CH4 substitution by CO2 (and N2) in the hydrate lattice. In this work, Mix3HRS is used to simulate the CO2 injection into a Class 2 hydrate accumulation characterized by a mobile aqueous phase underneath a hydrate bearing sediment. That type of hydrate reservoir is broadly confirmed in permafrost and along seashore. The production technique implies a two-stage approach using a two-well design, one for an injector and one for a producer. First, the CO2 is injected into the mobile aqueous phase to convert it into immobile CO2 hydrate and to initiate CH4 release from gas hydrate across the hydrate-water boundary (generally designating the onset of a hydrate stability zone). Second, CH4 hydrate decomposition is induced by the depressurization method at a producer to estimate gas production potential over 30 years. The conversion of the free water phase into the CO2 hydrate significantly reduces competitive water production in the second stage, thereby improving the methane gas production. A base case using only the depressurization stage is conducted to compare with enhanced gas production predicted by the CO2-assisted technique. The approach also offers a possibility to permanently store carbon dioxide in the underground formation to greater extent comparing to a direct injection of CO2 into gas hydrate sediment. Numerical models are based on the hydrate formations at the

  2. Role of different superplasticizers on hydrated lime pastes and mortars

    OpenAIRE

    Alvarez, J. I.; Fernandez, J M; Sirera, R. (Rafael); Perez-Nicolas, M. (María); Navarro-Blasco, I. (Íñigo); Duran, A

    2015-01-01

    The behaviour of different superplasticizers admixtures was assessed for hydrated lime pastes and mortars. Sometimes, air lime pastes and mortars were modified with two supplementary cementing materials (SCMs), namely nanosilica (NS) and metakaolin (MK). Two different polycarboxylate ethers, a lignosulfonate and a naphthalene condensed sulfonate superplasticizer were added to lime pastes and mortars and their effects on fresh-state properties as well as on the mechanical strengths were evalua...

  3. Nutrition and hydration concerns of the female football player

    OpenAIRE

    Maughan, Ronald J; Shirreffs, Susan M

    2007-01-01

    There is little information on the nutritional habits of female football players at any level of the game. There is also a shortage of information on the nutrition and hydration strategies that players should adopt. In general, differences in nutritional needs between males and females are smaller than differences between individuals, so that principles developed for male players also apply to women. There is a need to address energy balance and body composition: prolonged energy deficits can...

  4. Hydration and thermal strain during tennis in the heat

    OpenAIRE

    Bergeron, Michael F.

    2014-01-01

    Competitive tennis in the heat can prompt substantial sweat losses and extensive consequent body water and electrolyte deficits, as well as a level of thermal strain that considerably challenges a player's physiology, perception of effort, and on-court well-being and performance. Adequate hydration and optimal performance can be notably difficult to maintain when multiple same-day matches are played on successive days in hot weather. Despite the recognised effects of the heat, much more resea...

  5. Heavy Metal Desorption From Cement Hydrates Caused by Chloride Solutions

    OpenAIRE

    Hayashi, Akihiko; Ogawa, Yuko; Kawai, Kenji

    2014-01-01

    After the demolition of concrete structures, it is expected to recycle the whole of the demolished concrete. As of now, however, it is difficult to recycle the fine powders generated in the processes of demolition of concrete and manufacture of recycled aggregate because these powders may contain heavy metals exceeding the soil environmental standard, and such powders are disposed finally. It is well known that heavy metals are easily adsorbed on cement hydrates. To promote the total recyclin...

  6. Geometric changes of parotid glands caused by hydration during chemoradiotherapy

    International Nuclear Information System (INIS)

    Plan adaptation during the course of (chemo)radiotherapy of H&N cancer requires repeat CT scanning to capture anatomy changes such as parotid gland shrinkage. Hydration, applied to prevent nephrotoxicity from cisplatin, could temporarily alter the hydrogen balance and hence the captured anatomy. The aim of this study was to determine geometric changes of parotid glands as function of hydration during chemoradiotherapy compared to a control group treated with radiotherapy only. This study included an experimental group (n = 19) receiving chemoradiotherapy, and a control group (n = 19) receiving radiotherapy only. Chemoradiotherapy patients received cisplatin with 9 l of saline solution during hydration in the first, fourth and seventh week. The delineations of the parotid glands on the planning CT scan were automatically propagated to Cone Beam CT scans using deformable image registration. Relative volume and position of the parotid glands were determined at the second chemotherapy cycle (week four) and at fraction 35. When saline solution was administrated, the volume temporarily increased on the first day (7.2 %, p < 0.001), second day (10.8 %, p < 0.001) and third day (7.0 %, p = 0.016). The gland positions shifted lateral, the distance between glands increased on the first day with 1.5 mm (p < 0.001), on the second day 2.2 mm (p < 0.001). At fraction 35, with both groups the mean shrinkage was 24 % ± 11 % (1SD) and the mean medial distance between the parotid glands decreased by 0.47 cm ± 0.27 cm. Hydration significantly modulates parotid gland geometry. Unless, in the context of adaptive RT, a repeat CT scan is timed during a chemotherapy cycle, these effects are of minor clinical relevance

  7. Influence of ultra-fine fly ash on hydration shrinkage of cement paste

    Institute of Scientific and Technical Information of China (English)

    GAO Ying-li; ZHOU Shi-qiong

    2005-01-01

    Hydration shrinkage generated by cement hydration is the cause of autogenous shrinkage of high strength concrete. It may result in the volume change and even cracking of mortar and concrete. According to the data analysis in a series of experimental studies, the influence of ultra-fine fly ash on the hydration shrinkage of composite cementitious materials was investigated. It is found that ultra-fine fly ash can reduce the hydration shrinkage of cement paste effectively, and the more the ultra-fine fly ash, the less the hydration shrinkage. Compared with cement paste without the ultra-fine fly ash, the shrinkage ratio of cement paste reduces from 23.4% to 39.7% when the ultra-fine fly ash replaces cement from 20% to 50%. Moreover, the microscopic mechanism of the ultra-fine fly ash restraining the hydration shrinkage was also studied by scanning electron microscopy, X-ray diffraction and hydrated equations. The results show that the hydration shrinkage can be restrained to a certain degree because the ultra-fine fly ash does not participate in the hydration at the early stage and the secondary hydration products are different at the later stage.

  8. Application of gas hydrate formation in separation processes: A review of experimental studies

    International Nuclear Information System (INIS)

    Highlights: ► Review of gas hydrate technology applied to separation processes. ► Gas hydrates have potential to be a future sustainable separation technology. ► More theoretical, simulation, and economic studies needed. - Abstract: There has been a dramatic increase in gas hydrate research over the last decade. Interestingly, the research has not focussed on only the inhibition of gas hydrate formation, which is of particular relevance to the petroleum industry, but has evolved into investigations on the promotion of hydrate formation as a potential novel separation technology. Gas hydrate formation as a separation technology shows tremendous potential, both from a physical feasibility (in terms of effecting difficult separations) as well as an envisaged lower energy utilization criterion. It is therefore a technology that should be considered as a future sustainable technology and will find wide application, possibly replacing a number of current commercial separation processes. In this article, we focus on presenting a brief description of the positive applications of clathrate hydrates and a comprehensive survey of experimental studies performed on separation processes using gas hydrate formation technology. Although many investigations have been undertaken on the positive application of gas hydrates to date, there is a need to perform more theoretical, experimental, and economic studies to clarify various aspects of separation processes using clathrate/semi-clathrate hydrate formation phenomena, and to conclusively prove its sustainability.

  9. Measurements of methane hydrate equilibrium in systems inhibited with NaCl and methanol

    International Nuclear Information System (INIS)

    Highlights: ► We report phase equilibria data for hydrates with salt and methanol. ► A unique experimental procedure using the DSC is used for the measurements. ► Measured data suggest that current hydrate prediction models may need to be adjusted. - Abstract: Natural gas hydrates are ice-like inclusion compounds that form at high pressures and low temperatures in the presence of water and light hydrocarbons. Hydrate formation conditions are favorable in gas and oil pipelines, and their formation threatens gas and oil production. Thermodynamic hydrate inhibitors (THIs) are chemicals (e.g., methanol, monoethylene glycol) deployed in gas pipelines to depress the equilibrium temperature required for hydrate formation. This work presents a novel application of a stepwise differential scanning calorimeter (DSC) measurement to accurately determine the methane hydrate phase boundary in the presence of THIs. The scheme is first validated on a model (ice + salt water) system, and then generalized to measure hydrate equilibrium temperatures for pure systems and 0.035 mass fraction NaCl solutions diluted to 0, 0.05, 0.10, and 0.20 mass fraction methanol. The hydrate equilibrium temperatures are measured at methane pressures from (7.0 to 20.0) MPa. The measured equilibrium temperatures are compared to values computed by the predictive hydrate equilibrium tool CSMGem.

  10. The simulation of nature gas production from ocean gas hydrate reservoir by depressurization

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The vast amount of hydrocarbon gas encaged in gas hydrates is regarded as a kind of future potential energy supply due to its wide deposition and cleanness. How to exploit gas hydrate with safe, effective and economical methods is being pursued. In this paper, a mathematical model is developed to simulate the hydrate dissocia- tion by depressurization in hydrate-bearing porous medium. The model can be used to analyze the effects of the flow of multiphase fluids, the intrinsic kinetic process of hydrate dissociation, the endothermic process of hydrate dissociation, ice-water phase equilibrium, the variation of permeability, the convection and conduction on the hydrate dissociation and gas and water production. The nu- merical results agreed well with the 1-D and 2-D experiments. The numerical results for 3-D hydrate reservoir show that in the first stage of depressurization gas can be produced effectively from hydrate reservoir. With the depletion of reservoir energy because of endothermic process of hydrate dissociation the gas rate decreases rapidly. Then, methods such as thermal stimulation and inhibitor injection should be considered to replace depressurization

  11. Determination of the Physical Properties of Sediments Depending on Hydrate Saturation Using a "Quick Look" Method

    Science.gov (United States)

    Strauch, B.; Schicks, J. M.; Spangenberg, E.; Seyberth, K.; Heeschen, K. U.; Priegnitz, M.

    2015-12-01

    Seismic and electromagnetic measurements are promising tools for the detection and quantification of gas hydrate occurrences in nature. The seismic wave velocity depends among others on the hydrate quantity and the quality (e.g. pore filling or cementing hydrate). For a proper interpretation of seismic data the knowledge of the dependency of physical properties as a function of hydrate saturation in a certain scenario is crucial. Within the SUGAR III project we determine such dependencies for various scenarios to support models for joint inversion of seismic and EM data e.g. for the shallow gas hydrate reservoirs in the Danube Delta. Since the formation of artificial lab samples containing pore filling hydrate from methane dissolved in water is a complex and time consuming procedure, we developed an easier alternative. Ice is very similar to hydrate in some of its physical properties. Therefore it might be used as analogous pore fill in a "quick look" experiment to determine the dependency of rock physical properties on hydrate content. We used the freezing point depression of a KCl solution to generate a dependency of ice saturation on temperature. The measured seismic wave velocity in dependence on ice saturation compares very well with data measured on a glass bead sediment sample with methane hydrate formed from methane dissolved in water. We could also observe that ice, formed from a salt solution in the pore space of sediment, behaves similar to methane hydrate as a non-cementing solid pore fill.

  12. Summary and implications of the Mallik 2002 Gas Hydrate Production Research Well Program

    Energy Technology Data Exchange (ETDEWEB)

    Dallimore, S.R. [Geological Survey of Canada, Pacific Geoscience Centre, Sidney, BC (Canada); Collett, T.S. [United States Geological Survey, Denver, CO (United States)

    2005-07-01

    Fieldwork at the Mallik 2002 Gas Hydrate Production Research Well Program was conducted during the winter of 2001-2002, 30 years after the original Mallik L-38 discovery well. The field, which is in the Canadian Arctic at the edge of the Mackenzie Delta and the Beaufort Sea, has been shown to have one of the most concentrated gas hydrate deposits in the world. Exploratory wells have shown that almost all of the gas hydrate occurrences exist beneath 300 to 700 m of permafrost within unconsolidated or poorly consolidated sediments of Tertiary age. This paper summarized the scientific and engineering research conducted at the site. Insight was also provided on the implications of these results for the future production of natural gas from gas hydrate deposits and the evaluation of environmental conditions of terrestrial gas hydrate. Gas hydrate was described as being a crystalline solid consisting of gas molecules which may occur in terrestrial or marine accumulations. Interest in gas hydrate deposits as a fuel resource has grown in the past decade as conventional sources of natural gas decline. This paper outlined the petroleum resources in the Mackenzie Delta area. The management of the Mallik 2002 Gas Hydrate project was outlined with reference to the steering committee, the scientific and technical committee, and the international continental scientific drilling program. The 2002 Mallik field program involved surface geophysical surveys which identified gas hydrate occurrence in the JAPEX/JNOC/GSC et al. Mallik 5L-38 research well, and which delineated the gas hydrate zones. Geochemical and microbiology investigations were also conducted as part of the program. The structure and grain characteristics of gas hydrates were identified as well as gas hydrate properties in porous media. Geophysical surveys involved open-hole well logging, cross-well seismic surveys, and a study of geothermal regimes. The implications of climate change on gas hydrate occurrences was

  13. Adhesion force interactions between cyclopentane hydrate and physically and chemically modified surfaces.

    Science.gov (United States)

    Aman, Zachary M; Sloan, E Dendy; Sum, Amadeu K; Koh, Carolyn A

    2014-12-01

    Interfacial interactions between liquid-solid and solid-solid phases/surfaces are of fundamental importance to the formation of hydrate deposits in oil and gas pipelines. This work establishes the effect of five categories of physical and chemical modification to steel on clathrate hydrate adhesive force: oleamide, graphite, citric acid ester, nonanedithiol, and Rain-X anti-wetting agent. Hydrate adhesive forces were measured using a micromechanical force apparatus, under both dry and water-wet surface conditions. The results show that the graphite coating reduced hydrate-steel adhesion force by 79%, due to an increase in the water wetting angle from 42 ± 8° to 154 ± 7°. Two chemical surface coatings (nonanedithiol and the citric acid ester) induced rapid hydrate growth in the hydrate particles; nonanedithiol increased hydrate adhesive force by 49% from the baseline, while the citric acid ester coating reduced hydrate adhesion force by 98%. This result suggests that crystal growth may enable a strong adhesive pathway between hydrate and other crystalline structures, however this effect may be negated in cases where water-hydrocarbon interfacial tension is minimised. When a liquid water droplet was placed on the modified steel surfaces, the graphite and citric acid ester became less effective at reducing adhesive force. In pipelines containing a free water phase wetting the steel surface, chemical or physical surface modifications alone may be insufficient to eliminate hydrate deposition risk. In further tests, the citric acid ester reduced hydrate cohesive forces by 50%, suggesting mild activity as a hybrid anti-agglomerant suppressing both hydrate deposition and particle agglomeration. These results demonstrate a new capability to develop polyfunctional surfactants, which simultaneously limit the capability for hydrate particles to aggregate and deposit on the pipeline wall. PMID:25332072

  14. Hysteresis of methane hydrate formation/decomposition at subsea geological conditions

    International Nuclear Information System (INIS)

    Full text: Gas hydrates are a major risk when transporting oil and gas in offshore subsea pipelines. Under typical conditions in these pipelines (at high pressure and low temperature) the formation of gas hydrates is favourable. The hydrates form large solid plugs that can block pipelines and can even cause them to burst. This represents a major problem for the gas mining industry, which currently goes to extreme measures to reduce the risk of hydrate formation because there is no reliable experimental data on hydrate processes. The mechanisms of gas hydrate formation, growth and inhibition are poorly understood. A clear understanding of the fundamental processes will allow development of cost effective technologies to avoid production losses in gas pipelines. We are studying the nucleation of the methane hydrates by measuring the hysteresis of hydrate formation/decomposition by neutron diffraction. When a gas hydrate is decomposed (melted) the resulting water has a 'supposed memory effect' raising the probability of rapid hydrate reformation. This rapid reformation does not occur for pure water where nucleation can be delayed by several hours (induction time) due to metastability [1]. The memory effect can only be destroyed by extreme heating of the effected area. Possible causes of this effect include residual water structure, persistent hydrate crystal lites remaining in solution and remaining dissolved gas. We will compare the kinetics of formation and the stability region of hydrate formation of 'memory' water for comparison with pure water. This information has important implications for the oil and gas industry because it should provide a better understanding of the role of multiple dissociation and reformation of gas hydrates in plug formation.

  15. Permafrost-associated gas hydrates of Northern Alaska: A possible source of atmospheric methane

    International Nuclear Information System (INIS)

    Numerous researchers have suggested that destabilized gas hydrates may be contributing to this buildup in atmospheric methane. Little is known about the geologic or geochemical nature of gas hydrates, even though they are known to occur in numerous arctic sedimentary basins. Because of the abundance of available geologic data, the author's research has focused on assessing the distribution of gas hydrates within the onshore regions of northern Alaska; currently, onshore permafrost-associated gas hydrates are believed to be insulated from most atmospheric temperature changes and are not at this time an important source of atmospheric methane. Their onshore gas hydrate studies, however, can be used to develop geologic analogs for potential gas hydrate occurrences within unexplored areas, such as the thermally unstable nearshore continental shelf. On the North Slope, gas hydrates have been identified in 36 industry wells by using well-log responses calibrated to the response of an interval in one well where gas hydrates were recovered in a core by an oil company. Most gas hydrates they identified occur in six laterally continuous Upper Cretaceous and lower Tertiary sandstone and conglomerate units; all these hydrates are geographically restricted to the area overlying the eastern part of the Kuparuk River Oil Field and the western part of the Prudhoe Bay Oil Field. Stable carbon isotope geochemical analysis of well cuttings suggests that the identified hydrates originated from a mixture of deep-source thermogenic gas and shallow microbial gas that was either directly converted to gas hydrate or first concentrated in existing traps and later converted to gas hydrate. They postulate that the thermogenic gas migrated from deeper reservoirs along the faults thought to be migration pathways for the large volumes of shallow, heavy oil found in the same area

  16. Hydration of protonated aromatic amino acids: phenylalanine, tryptophan, and tyrosine.

    Science.gov (United States)

    Gao, Bing; Wyttenbach, Thomas; Bowers, Michael T

    2009-04-01

    The first steps of hydration of the protonated aromatic amino acids phenylalanine, tryptophan, and tyrosine were studied experimentally employing a mass spectrometer equipped with a drift cell to examine the sequential addition of individual water molecules in equilibrium experiments and theoretically by a combination of molecular mechanics and electronic structure calculations (B3LYP/6-311++G**) on the three amino acid systems including up to five water molecules. It is found that both the ammonium and carboxyl groups offer good water binding sites with binding energies of the order of 13 kcal/mol for the first water molecule. Subsequent water molecules bind less strongly, in the range of 7-11 kcal/mol for the second through fifth water molecules. The ammonium group is able to host up to three water molecules and the carboxyl group one water molecule before additional water molecules bind either to the amino acid side chain as in tyrosine or to already-bound water in a second solvation shell around the ammonium group. Reasons for the surprisingly high water affinity of the neutral carboxyl group, comparable to that of the charge-carrying ammonium group, are found to be high intrinsic hydrophilicity, favorable charge-dipole alignment, and--for the case of multiply hydrated species--favorable dipole-dipole interaction among water molecules and the lack of alternative fully exposed hydration sites.

  17. Hydration and rotational diffusion of levoglucosan in aqueous solutions.

    Science.gov (United States)

    Corezzi, S; Sassi, P; Paolantoni, M; Comez, L; Morresi, A; Fioretto, D

    2014-05-14

    Extended frequency range depolarized light scattering measurements of water-levoglucosan solutions are reported at different concentrations and temperatures to assess the effect of the presence and distribution of hydroxyl groups on the dynamics of hydration water. The anhydro bridge, reducing from five to three the number of hydroxyl groups with respect to glucose, considerably affects the hydration properties of levoglucosan with respect to those of mono and disaccharides. In particular, we find that the average retardation of water dynamics is ≈3-4, that is lower than ≈5-6 previously found in glucose, fructose, trehalose, and sucrose. Conversely, the average number of retarded water molecules around levoglucosan is 24, almost double that found in water-glucose mixtures. These results suggest that the ability of sugar molecules to form H-bonds through hydroxyl groups with surrounding water, while producing a more effective retardation, it drastically reduces the spatial extent of the perturbation on the H-bond network. In addition, the analysis of the concentration dependence of the hydration number reveals the aptitude of levoglucosan to produce large aggregates in solution. The analysis of shear viscosity and rotational diffusion time suggests a very short lifetime for these aggregates, typically faster than ≈20 ps. PMID:24832286

  18. Hydration biomarkers and dietary fluid consumption of women.

    Science.gov (United States)

    Armstrong, Lawrence E; Johnson, Evan C; Munoz, Colleen X; Swokla, Brittany; Le Bellego, Laurent; Jimenez, Liliana; Casa, Douglas J; Maresh, Carl M

    2012-07-01

    Normative values and confidence intervals for the hydration indices of women do not exist. Also, few publications have precisely described the fluid types and volumes that women consume. This investigation computed seven numerical reference categories for widely used hydration biomarkers (eg, serum and urine osmolality) and the dietary fluid preferences of self-reported healthy, active women. Participants (n=32; age 20±1 years; body mass 59.6±8.5 kg; body mass index [calculated as kg/m(2)] 21.1±2.4) were counseled in the methods to record daily food and fluid intake on 2 consecutive days. To reduce day-to-day body water fluctuations, participants were tested only during the placebo phase of the oral contraceptive pill pack. Euhydration was represented by the following ranges: serum osmolality=293 to 294 mOsm/kg; mean 24-hour total fluid intake=2,109 to 2,506 mL/24 hours; mean 24-hour total beverage intake=1,300 to 1,831 mL/24 hours; urine volume=951 to 1,239 mL/24 hours; urine specific gravity=1.016 to 1.020; urine osmolality=549 to 705 mOsm/kg; and urine color=5. However, only 3% of women experienced a urine specific gravity hyperhydration, euhydration, and dehydration that can be used by registered dietitians and clinicians to counsel women about their hydration status. PMID:22889635

  19. Hydration and rotational diffusion of levoglucosan in aqueous solutions

    Science.gov (United States)

    Corezzi, S.; Sassi, P.; Paolantoni, M.; Comez, L.; Morresi, A.; Fioretto, D.

    2014-05-01

    Extended frequency range depolarized light scattering measurements of water-levoglucosan solutions are reported at different concentrations and temperatures to assess the effect of the presence and distribution of hydroxyl groups on the dynamics of hydration water. The anhydro bridge, reducing from five to three the number of hydroxyl groups with respect to glucose, considerably affects the hydration properties of levoglucosan with respect to those of mono and disaccharides. In particular, we find that the average retardation of water dynamics is ≈3-4, that is lower than ≈5-6 previously found in glucose, fructose, trehalose, and sucrose. Conversely, the average number of retarded water molecules around levoglucosan is 24, almost double that found in water-glucose mixtures. These results suggest that the ability of sugar molecules to form H-bonds through hydroxyl groups with surrounding water, while producing a more effective retardation, it drastically reduces the spatial extent of the perturbation on the H-bond network. In addition, the analysis of the concentration dependence of the hydration number reveals the aptitude of levoglucosan to produce large aggregates in solution. The analysis of shear viscosity and rotational diffusion time suggests a very short lifetime for these aggregates, typically faster than ≈20 ps.

  20. Effects of hydration and physical therapy on tracheal transport velocity

    International Nuclear Information System (INIS)

    A new tracer method for quantitative measurements of tracheal transport velocity (TTV) in mm/min in dogs has been described recently. Using the same technique, the effects of dehydration, hydration, postural drainage and physical therapy on TTV were studied. There was a significant (p < 0.05) reduction in TTV following dehydration and these values reverted to normal with hydration in all ten dogs. Tracheal transport velocity increased on the average of 39.7 percent with a mean change of 7.7 mm/min (p < 0.01) following postural drainage in seven dogs. On the other hand, TTV increased on the average of 51 percent with a mean change of 8.2 mm/min (p <0.01) following chest percussion in six dogs. Postural drainage and chest percussion each increased TTV significantly beyond the base-line values. However, hydration only restored TTV to base-line values when applied to dogs in the hydropenic state. These therapeutic measures have been used empirically in the past. The present study gives objective evidence of their beneficial effects in dogs and suggests that such treatments may have a definite scientific basis for clinical application in chronic obstructive airways disease

  1. Simulation experiments on gas production from hydrate-bearing sediments

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Experiments were made on 58 sediment samples from four sites(1244,1245,1250 and 1251) of ODP204 at five temperature points(25,35,45,55 and 65℃) to simulate methane production from hydrate-bearing sediments.Simulation results from site 1244 show that the gas components consist mainly of methane and carbon dioxide,and heavy hydrocarbons more than C2+ cannot be detected.This site also gives results,similar to those from the other three,that the methane production is controlled by experimental temperatures,generally reaching the maximum gas yields per gram sediment or TOC under lower temperatures(25 and 35 ℃).In other words,the methane amount could be related to the buried depth of sediments,given the close relation between the depth and temperature.Sediments less than 1200 m below seafloor are inferred to still act as a biogenic gas producer to pour methane into the present hydrate zone,while sedimentary layers more than 1200 m below seafloor have become too biogenically exhausted to offer any biogas,but instead they produce thermogenic gas to give additional supply to the hydrate formation in the study area.

  2. Acoustic emissions correlated with hydration of Saguaro Cactus

    Science.gov (United States)

    Wardell, L. J.; Rowe, C. A.

    2013-12-01

    For some years it has been demonstrated that hardwood trees produce acoustic emissions during periods of drought, which arise from cavitation in the xylem as water is withdrawn. These emissions not only provide insights into the fluid transport behavior within these trees, but also the degree to which cavitation can proceed before inevitable tree mortality. Such studies can have significant impact on our understanding of forest die-off in the face of climate change. Plant mortality is not limited to woody trees, however, and it is not only the coniferous and deciduous forests whose response to climate and rainfall changes are important. In the desert Southwest we observe changes to survival rates of numerous species of flora. One of the most conspicuous of these plants is the iconic Saguaro Cactus (Carnegiea gigantean). These behemoths of the Sonoran Desert are very sensitive to small perturbations in their environment. Specifically, during the summer monsoon season when the cacti become well-hydrated, they can absorb hundreds of gallons of water within a very short time frame. We have obtained a juvenile saguaro on which we are conducting experiments to monitor acoustic emissions during hydration and dessication cycles. We will report on our observations obtained using piezoelectric ceramic accelerometers whose signals are digitized up to 44 Khz and recorded during hydration.

  3. Order and disorder in calcium–silicate–hydrate

    International Nuclear Information System (INIS)

    Despite advances in the characterization and modeling of cement hydrates, the atomic order in Calcium–Silicate–Hydrate (C–S–H), the binding phase of cement, remains an open question. Indeed, in contrast to the former crystalline model, recent molecular models suggest that the nanoscale structure of C–S–H is amorphous. To elucidate this issue, we analyzed the structure of a realistic simulated model of C–S–H, and compared the latter to crystalline tobermorite, a natural analogue of C–S–H, and to an artificial ideal glass. The results clearly indicate that C–S–H appears as amorphous, when averaged on all atoms. However, an analysis of the order around each atomic species reveals that its structure shows an intermediate degree of order, retaining some characteristics of the crystal while acquiring an overall glass-like disorder. Thanks to a detailed quantification of order and disorder, we show that, while C–S–H retains some signatures of a tobermorite-like layered structure, hydrated species are completely amorphous

  4. Computational phase diagrams of noble gas hydrates under pressure

    Energy Technology Data Exchange (ETDEWEB)

    Teeratchanan, Pattanasak, E-mail: s1270872@sms.ed.ac.uk; Hermann, Andreas, E-mail: a.hermann@ed.ac.uk [Centre for Science at Extreme Conditions and SUPA, School of Physics and Astronomy, The University of Edinburgh, Edinburgh EH9 3FD (United Kingdom)

    2015-10-21

    We present results from a first-principles study on the stability of noble gas-water compounds in the pressure range 0-100 kbar. Filled-ice structures based on the host water networks ice-I{sub h}, ice-I{sub c}, ice-II, and C{sub 0} interacting with guest species He, Ne, and Ar are investigated, using density functional theory (DFT) with four different exchange-correlation functionals that include dispersion effects to various degrees: the non-local density-based optPBE-van der Waals (vdW) and rPW86-vdW2 functionals, the semi-empirical D2 atom pair correction, and the semi-local PBE functional. In the He-water system, the sequence of stable phases closely matches that seen in the hydrogen hydrates, a guest species of comparable size. In the Ne-water system, we predict a novel hydrate structure based on the C{sub 0} water network to be stable or at least competitive at relatively low pressure. In the Ar-water system, as expected, no filled-ice phases are stable; however, a partially occupied Ar-C{sub 0} hydrate structure is metastable with respect to the constituents. The ability of the different DFT functionals to describe the weak host-guest interactions is analysed and compared to coupled cluster results on gas phase systems.

  5. Temperature effects in deep-water hydrate foam

    CERN Document Server

    Egorov, Alexander V; Rozhkov, Aleksey N

    2016-01-01

    This study focuses on heat and mass exchange processes in hydrate foam during its formation from methane bubbles in gas hydrate stability zone (GHSZ) of the Lake Baikal and following delivery of it in open container to the lake surface. The foam was formed as a result of methane bubble collection with a trap/container. The trap was inverted glass beaker of diameter of 70 mm and 360 mm long. Open bottom end of the beaker used as enter for bubbles ascended from the lakebed. At a depth of 1400 m all bubbles which fed to the trap were transformed here into solid hydrate foam. The sensitive thermometer was mounted in the middle of the trap and recorded the temperature inside trap. The fate of the bubbles in the trap was recorded by video-camera. During ascend within GHSZ with velocity of about 0.375 m/s we observed the continuous decrease of the temperature in the foam up to a level of negative magnitude in a depth interval of 1400 - 750 meters. Above 750 m temperature decrease was changed by small growth. However...

  6. Active iron-rich belite sulfoaluminate cements: clinkering and hydration.

    Science.gov (United States)

    Cuberos, Antonio J M; De la Torre, Angeles G; Alvarez-Pinazo, G; Martín-Sedeño, M Carmen; Schollbach, Katrin; Pöllmann, Herbert; Aranda, Miguel A G

    2010-09-01

    Ordinary Portland cement (OPC) is an environmentally contentious material, as for every ton of OPC produced, on average, 0.97 tons of CO2 are released. Conversely, belite sulfoaluminate (BSA) cements are promising eco-friendly building materials, as their production may deplete CO2 emissions up to 35% (compared to OPC). However, the hydration rate of belite is slow. Here, we report the clinkering of iron-rich BSA materials, their activation with B2O3, and establishing a methodology to measure their improved reactivities. Nonactivated BSA clinker contained only beta belite phase, 52 wt %. Meanwhile, BSA clinkers activated with 1 and 2 wt % of B2O3 contained 28 wt % of beta and 25 wt % of alpha'H; and 54 wt % of alpha'H phase, respectively. Therefore, activation of BSA has been proved as alpha'H-belite is stabilized. The hydration of the cements has been studied by laboratory and synchrotron X-ray powder diffraction (using Rietveld method and chemical constraints), calorimetry, and environmental scanning electron microscopy. Cement pastes have different hydration rates. For nonactivated BSA cement, 20 and 48% of the belite reacted after one and three months, respectively. Conversely, 37-49% after one month and 52-62% after three months of overall belite reactivities have been measured for BSA cements activated with B2O3. PMID:20701316

  7. Hydration and urinary pseudoephedrine levels after a simulated team game.

    Science.gov (United States)

    Jolley, Daniel; Dawson, Brian; Maloney, Shane K; White, James; Goodman, Carmel; Peeling, Peter

    2014-06-01

    This study investigated the influence of dehydration on urinary levels of pseudoephedrine (PSE) after prolonged repeated effort activity. Fourteen athletes performed a simulated team game circuit (STGC) outdoors over 120 min under three different hydration protocols: hydrated (HYD), dehydrated (DHY) and dehydrated + postexercise fluid bolus (BOL). In all trials, a 60 mg dose of PSE was administered 30 min before trial and at half time of the STGC. Urinary PSE levels were measured before drug administration and at 90 min postexercise. In addition, body mass (BM) changes and urinary specific gravity (USG), osmolality (OSM), creatinine (Cr), and pH values were recorded. No differences in PSE levels were found 90 min postexercise between conditions (HYD: 208.5 ± 116.5; DHY: 238.9 ± 93.5; BOL: 195.6 ± 107.3 μg · ml(-1)), although large variations were seen within and between participants across conditions (range: 33-475 μg · ml(-1): ICC r = .03-0.16, p > .05). There were no differences between conditions in USG, OSM, pH or PSE/Cr ratio. In conclusion, hydration status did not influence urinary PSE levels after prolonged repeated effort activity, with ~70% of samples greater than the WADA limit (>150 μg · ml(-1)), and ~30% under. Due to the unpredictability of urinary PSE values, athletes should avoid taking any medications containing PSE during competition.

  8. A new approach to calculate the hydration of DNA molecules

    Energy Technology Data Exchange (ETDEWEB)

    Hummer, G. [Los Alamos National Lab., NM (United States); Soumpasis, D.M. [Max-Planck-Institut fuer Biophysikalische Chemie (Karl-Friedrich-Bonhoeffer-Institut), Goettingen (Germany)

    1993-09-01

    A new method to calculate approximate water density distributions around DNA is presented. Formal and computational simplicity are emphasized in order to allow routine hydration studies. The method is based on the application of pair and triplet correlation functions of water-oxygen calculated by computer simulation. These correlation functions are combined with the configurational data of the electronegative atoms on DNA (oxygen and nitrogen) taken from crystal structures. For three B-DNA structures water density distributions are calculated and discussed. The observed characteristic features agree well with the prevalent picture from experiments. The minor groove shows a more structured hydration than the major groove. Also, the minor groove hydration of A{center_dot}T basepair tracts differs from that found in G{center_dot}C basepair regions. In A{center_dot}T tracts single peaks of high water density appear, whereas in G{center_dot}C regions the minor groove is occupied by two side-by-side ribbons of water.

  9. HYDRATION AND PROPERTIES OF BLENDED CEMENT SYSTEMS INCORPORATING INDUSTRIAL WASTES

    Directory of Open Access Journals (Sweden)

    Heikal M.

    2013-06-01

    Full Text Available This paper aims to study the characteristics of ternary blended system, namely granulated blast-furnace slag (WCS, from iron steel company and Homra (GCB from Misr Brick (Helwan, Egypt and silica fume (SF at 30 mass % pozzolanas and 70 mass % OPC. The required water of standard consistency and setting times were measured as well as physico-chemical and mechanical characteristics of the hardened cement pastes were investigated. Some selected cement pastes were tested by TGA, DTA and FT-IR techniques to investigate the variation of hydrated products of blended cements. The pozzolanic activity of SF is higher than GCB and WCS. The higher activity of SF is mainly due to its higher surface area than the other two pozzolanic materials. On the other side, GCB is more pozzolanic than WCS due to GCB containing crystalline silica quartz in addition to an amorphous phase. The silica quartz acts as nucleating agents which accelerate the rate of hydration in addition to its amorphous phase, which can react with liberating Ca(OH2 forming additional hydration products.

  10. Correlation Between Chain Architecture and Hydration Water Structure in Polysaccharides.

    Science.gov (United States)

    Grossutti, Michael; Dutcher, John R

    2016-03-14

    The physical properties of confined water can differ dramatically from those of bulk water. Hydration water associated with polysaccharides provides a particularly interesting example of confined water, because differences in polysaccharide structure provide different spatially confined environments for water sorption. We have used attenuated total reflection infrared (ATR-IR) spectroscopy to investigate the structure of hydration water in films of three different polysaccharides under controlled relative humidity (RH) conditions. We compare the results obtained for films of highly branched, dendrimer-like phytoglycogen nanoparticles to those obtained for two unbranched polysaccharides, hyaluronic acid (HA), and chitosan. We find similarities between the water structuring in the two linear polysaccharides and significant differences for phytoglycogen. In particular, the results suggest that the high degree of branching in phytoglycogen leads to a much more well-ordered water structure (low density, high connectivity network water), indicating the strong influence of chain architecture on the structuring of water. These measurements provide unique insight into the relationship between the structure and hydration of polysaccharides, which is important for understanding and exploiting these sustainable nanomaterials in a wide range of applications.

  11. Removal of phosphate from greenhouse wastewater using hydrated lime.

    Science.gov (United States)

    Dunets, C Siobhan; Zheng, Youbin

    2014-01-01

    Phosphate (P) contamination in nutrient-laden wastewater is currently a major topic of discussion in the North American greenhouse industry. Precipitation of P as calcium phosphate minerals using hydrated lime could provide a simple, inexpensive method for retrieval. A combination of batch experiments and chemical equilibrium modelling was used to confirm the viability of this P removal method and determine lime addition rates and pH requirements for greenhouse wastewater of varying nutrient compositions. Lime: P ratio (molar ratio of CaMg(OH)₄: PO₄‒P) provided a consistent parameter for estimating lime addition requirements regardless of initial P concentration, with a ratio of 1.5 providing around 99% removal of dissolved P. Optimal P removal occurred when lime addition increased the pH from 8.6 to 9.0, suggesting that pH monitoring during the P removal process could provide a simple method for ensuring consistent adherence to P removal standards. A Visual MINTEQ model, validated using experimental data, provided a means of predicting lime addition and pH requirements as influenced by changes in other parameters of the lime-wastewater system (e.g. calcium concentration, temperature, and initial wastewater pH). Hydrated lime addition did not contribute to the removal of macronutrient elements such as nitrate and ammonium, but did decrease the concentration of some micronutrients. This study provides basic guidance for greenhouse operators to use hydrated lime for phosphate removal from greenhouse wastewater. PMID:25176490

  12. Correlation Between Chain Architecture and Hydration Water Structure in Polysaccharides.

    Science.gov (United States)

    Grossutti, Michael; Dutcher, John R

    2016-03-14

    The physical properties of confined water can differ dramatically from those of bulk water. Hydration water associated with polysaccharides provides a particularly interesting example of confined water, because differences in polysaccharide structure provide different spatially confined environments for water sorption. We have used attenuated total reflection infrared (ATR-IR) spectroscopy to investigate the structure of hydration water in films of three different polysaccharides under controlled relative humidity (RH) conditions. We compare the results obtained for films of highly branched, dendrimer-like phytoglycogen nanoparticles to those obtained for two unbranched polysaccharides, hyaluronic acid (HA), and chitosan. We find similarities between the water structuring in the two linear polysaccharides and significant differences for phytoglycogen. In particular, the results suggest that the high degree of branching in phytoglycogen leads to a much more well-ordered water structure (low density, high connectivity network water), indicating the strong influence of chain architecture on the structuring of water. These measurements provide unique insight into the relationship between the structure and hydration of polysaccharides, which is important for understanding and exploiting these sustainable nanomaterials in a wide range of applications. PMID:26859153

  13. Comparative measurement of hydration effects of herbal moisturizers

    Directory of Open Access Journals (Sweden)

    Swarnlata Saraf

    2010-01-01

    Full Text Available Improvements of skin hydration properties by the use of polyherbal moisturizers are the recent advances in cosmetic preparations to avoid the harmful effects of chemical moisturizers. The main aim of the study was to establish selection preference of different available marketed herbal moisturizers on the basis of the efficiency of constituents for their hydration effects. The criteria for the selection of formulations were presence of herbal constituents, wheat germ oil and Aloe vera extract. Initially, physiochemical and psychometric studies were performed to visualize the compliance of moisturizers with the skin. The clinical study was carried out in six groups of six healthy human volunteers (aged 20-25 years each applying moisturizers twice daily over a period of 3 weeks in their forearm. The skin properties measured were conductance, glow and appearance. The results indicated that all the moisturizers show moisturizing effect in a time-dependent pattern and the maximum increase in skin conductance was 168.125 and 165.24% for A2 and A1, respectively. Ranking of moisturizers based on conductance as well as physicochemical analysis is A2 > A1 > A4 > A3 > A5 > A6. It was found that the formulation A2 having wheat germ oil, Aloe vera extract and turmeric extract in combination showed best results due to their synergistic effect and wheat germ oil or Aloe extract, when present separately produced skin hydration to lesser extent.

  14. Ionic conduction in different hydrated V2O5 film

    Science.gov (United States)

    Saatci, A. Evrim; Gökdemir, F. Pınar; Menda, U. Deneb; Kavak, Pelin; Özdemir, Orhan; Kutlu, Kubilay

    2012-09-01

    Because of the layered structure of vanadium pentoxide films (V2O5), approved by XRD measurement, sensitized from different hydrated V2O5.nH2O sols, demonstrated anisotropic conductivities in current voltage (I-V) measurement. Conductivity values, originated from electronic and ionic conductions, differed provided that measurements were performed in a direction parallel to the ribbons rather than perpendicular to them. The overall electrical conductivity of V2O5nH2O sols mainly depended on the hydration state n and the amount of reduced V4+ ions in which n was determined around 4-6 [1] from the basal distance (17.6 Å) through XRD measurement while V4+ ions were determined through FTIR analysis. Electronic conduction prevailed in dehydrated V2O50.5H2O sols whereas non-stoichiometric vanadium pentoxide was a mixed-valence compound and its electronic properties arised from electron hopping between V4+ and V5+ ions so-called "small polaron model". Indeed, reduction/oxidation peaks in lithium (Li+) intercalation by cyclic voltammograms (CV) indicated the V4+ and V5+ ions in V2O5 sols. Temperature dependent I-V analysis showed Arheniuss type activation energy, EA, and located in between 0.3-0.5 eV; proposing ionic conduction rather than electronic conduction, specifically proton diffusion in V2O5 film. Indeed, hydration state greater than 0.5 predicted ionic conduction [1].

  15. Dry-grinded ultrafine cements hydration. physicochemical and microstructural characterization

    Directory of Open Access Journals (Sweden)

    Foteini Kontoleontos

    2013-04-01

    Full Text Available The aim of the present research work was the evaluation of the physicochemical and microstructural properties of two ultrafine cements, produced by dry grinding of a commercial CEM I 42.5N cement. The effect of grinding on particle size distribution was determined by laser scattering analyzer. All cements were tested for initial and final setting times, consistency of standard paste, soundness, flow of normal mortar and compressive strengths after 1, 2, 7 and 28 days. The effect of the fineness on the heat of hydration was also investigated. The hydration products were determined by X-ray diffraction analysis and by Fourier transform infrared spectroscopy, at 1, 2, 7 and 28 days. The microstructure of the hardened cement pastes and their morphological characteristics were examined by scanning electron microscopy. Porosity and pore size distribution were evaluated by mercury intrusion porosimetry. The effects of greater fineness on compressive strengths were evident principally at early ages. After the first 24 hours of hydration, the compressive strength of the finest cements was about 3 times higher (over 48 MPa than the corresponding of CEM I 42.5N (15.1 MPa.

  16. Porous and adsorption properties of hydrated cement paste

    Directory of Open Access Journals (Sweden)

    Marina Biljana S.

    2004-01-01

    Full Text Available Adsorption isotherms of benzene on hydrated cement pastes prepared by cement ground with and without the addition of grinding aids, triethanol amine (TEA and ethylene glycol (EG were investigated. The adsorption isotherms were interpreted by means of the Dubinin-Astakhov (DA and Dubinin-Radushkevich-Stoeckli (DRS equations. The microporous structure of cement gel (C-S-H in the cement pastes, and changes in the Gibbs free energy of adsorption were determined. The mechanical properties of the cement pastes were also measured. It was evident that pastes with additives had different parameters of the DRS and DA equations: the volume and dimensions of the gel pores, the distribution of the dimensions, the characteristic energy of adsorption, and the change in the Gibbs free energy of adsorption. The mechanical properties were also different. The dispersity of the additive-containing ground cements had a favorable effect on the hydration processes. When applying TEA, it was also necessary to analyze its influence on the chemical behavior of hydration in the starting period.

  17. CO2 + N2O mixture gas hydrate formation kinetics and effect of soil minerals on mixture-gas hydrate formation process

    Science.gov (United States)

    Enkh-Amgalan, T.; Kyung, D.; Lee, W.

    2012-12-01

    CO2 mitigation is one of the most pressing global scientific topics in last 30 years. Nitrous oxide (N2O) is one of the main greenhouse gases (GHGs) defined by the Kyoto Protocol and its global warming potential (GWP) of one metric ton is equivalent to 310 metric tons of CO2. They have similar physical and chemical properties and therefore, mixture-gas (50% CO2 + 50% N2O) hydrate formation process was studied experimentally and computationally. There were no significant research to reduce N20 gas and we tried to make hydrate to mitigate N20 and CO2 in same time. Mixture gas hydrate formation periods were approximately two times faster than pure N2O hydrate formation kinetic in general. The fastest induction time of mixture-gas hydrate formation observed in Illite and Quartz among various soil mineral suspensions. It was also observed that hydrate formation kinetic was faster with clay mineral suspensions such as Nontronite, Sphalerite and Montmorillonite. Temperature and pressure change were not significant on hydrate formation kinetic; however, induction time can be significantly affected by various chemical species forming under the different suspension pHs. The distribution of chemical species in each mineral suspension was estimated by a chemical equilibrium model, PHREEQC, and used for the identification of hydrate formation characteristics in the suspensions. With the experimental limitations, a study on the molecular scale modeling has a great importance for the prediction of phase behavior of the gas hydrates. We have also performed molecular dynamics computer simulations on N2O and CO2 hydrate structures to estimate the residual free energy of two-phase (hydrate cage and guest molecule) at three different temperature ranges of 260K, 273K, and 280K. The calculation result implies that N2O hydrates are thermodynamically stable at real-world gas hydrate existing condition within given temperature and pressure. This phenomenon proves that mixture-gas could be

  18. Synthesis and characterization of uranium (IV) phosphate-hydrogenphosphate hydrate and cerium (IV) phosphate-hydrogenphosphate hydrate

    Science.gov (United States)

    Brandel, V.; Clavier, N.; Dacheux, N.

    2005-04-01

    A new uranium (IV) phosphate of proposed formula U 2(PO 4) 2HPO 4·H 2O, i.e. uranium phosphate-hydrogenphosphate hydrate (UPHPH), was synthesized in autoclave and/or in polytetrafluoroethylene closed containers at 150 °C by three ways: from uranium (IV) hydrochloric solution and phosphoric acid, from uranium dioxide and phosphoric acid and by transformation of the uranium hydrogenphosphate hydrate U(HPO 4) 2· nH 2O. The new product appears similar to the previously published thorium phosphate-hydrogenphosphate hydrate Th 2(PO 4) 2HPO 4·H 2O (TPHPH). From preliminary studies, it was found that UPHPH crystallizes in monoclinic system ( a=2.1148(7) nm, b=0.6611(2) nm, c=0.6990(3) nm, β=91.67(3)° and V=0.9768(10) nm). Heated under inert atmosphere, this compound is decomposed above 400 °C into uranium phosphate-triphosphate U 2(PO 4)P 3O 10, uranium diphosphate α-UP 2O 7 and diuranium oxide phosphate U 2O(PO 4) 2. Crystallized cerium (IV) phosphate-hydrogenphosphate hydrate Ce 2(PO 4) 2HPO 4·H 2O (CePHPH) was also synthesized from (NH 4) 2Ce(NO 3) 6 and phosphoric acid solutions by the same method (monoclinic system: a=2.1045(5) nm, b=0.6561(2) nm, c=0.6949(2) nm, β=91.98(1)° and V=0.9588(9) nm). When heating above 600 °C, cerium (IV) is reduced into Ce (III) and forms a mixture of CePO 4 (monazite structure) and CeP 3O 9.

  19. The impact of permafrost-associated microorganisms on hydrate formation kinetics

    Science.gov (United States)

    Luzi-Helbing, Manja; Liebner, Susanne; Spangenberg, Erik; Wagner, Dirk; Schicks, Judith M.

    2016-04-01

    The relationship between gas hydrates, microorganisms and the surrounding sediment is extremely complex: On the one hand, microorganisms producing methane provide the prerequisite for gas hydrate formation. As it is known most of the gas incorporated into natural gas hydrates originates from biogenic sources. On the other hand, as a result of microbial activity gas hydrates are surrounded by a great variety of organic compounds which are not incorporated into the hydrate structure but may influence the formation or degradation process. For gas hydrate samples from marine environments such as the Gulf of Mexico a direct association between microbes and gas hydrates was shown by Lanoil et al. 2001. It is further assumed that microorganisms living within the gas hydrate stability zone produce biosurfactants which were found to enhance the hydrate formation process significantly and act as nucleation centres (Roger et al. 2007). Another source of organic compounds is sediment organic matter (SOM) originating from plant material or animal remains which may also enhance hydrate growth. So far, the studies regarding this relationship were focused on a marine environment. The scope of this work is to extend the investigations to microbes originating from permafrost areas. To understand the influence of microbial activity in a permafrost environment on the methane hydrate formation process and the stability conditions of the resulting hydrate phase we will perform laboratory studies. Thereby, we mimic gas hydrate formation in the presence and absence of methanogenic archaea (e.g. Methanosarcina soligelidi) and other psychrophilic bacteria isolated from permafrost environments of the Arctic and Antarctic to investigate their impact on hydrate induction time and formation rates. Our results may contribute to understand and predict the occurrences and behaviour of potential gas hydrates within or adjacent to the permafrost. Lanoil BD, Sassen R, La Duc MT, Sweet ST, Nealson KH

  20. Observation of ice sheet formation on methane and ethane gas hydrates using a scanning confocal microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Nagao, J.; Shimomura, N.; Ebinuma, T.; Narita, H. [National Inst. of Advanced Industrial Science and Technology, Toyohira, Sapporo (Japan). Methane Hydrate Research Lab.

    2008-07-01

    Interest in gas hydrates has increased in recent years due to the discovery of large deposits under the ocean floor and in permafrost regions. Natural gas hydrates, including methane, is expected to become a new energy source and a medium for energy storage and transportation. Gas hydrates consist of an open network of water molecules that are hydrogen-bonded in a similar manner to ice. Gas molecules are interstitially engaged under high pressures and low temperatures. Although the dissociation temperature of methane hydrate under atmospheric pressure is about 193 K, studies have shown that methane hydrate can be stored at atmospheric pressure and 267 K for 2 years. Because of this phenomenon, known as self-preservation, transportation and storage of methane hydrate can occur at temperature conditions milder than those for liquefied methane gas at atmospheric pressure. This study examined the surface changes of methane and ethane hydrates during dissociation using an optical microscope and confocal scanning microscope (CSM). This paper reported on the results when the atmospheric gas pressure was decreased. Ice sheets formed on the surfaces of methane and ethane gas hydrates due to depressurizing dissociation of methane and ethane hydrates when the methane and ethane gas pressures were decreased at designated temperatures. The dissociation of methane gas hydrate below below 237 K resulted in the generation of small ice particles on the hydrate surface. A transparent ice sheet formed on the hydrate surface above 242 K. The thickness of the ice sheet on the methane hydrate surface showed the maximum of ca. 30 {mu}m at 253 K. In the case of ethane hydrates, ice particles and ice sheets formed below 262 and 267 respectively. Since the ice particles and ice sheets were formed by water molecules generated during the gas hydrate dissociation, the mechanism of ice sheet formation depends on the dissociation rate of hydrate, ice particle sintering rate, and water molecule